CN103296163B - led - Google Patents

Abstract

The invention discloses a variety of light-emitting diodes. The light-emitting diodes include a sapphire substrate, an N-type semiconductor layer, an active layer, a P-type semiconductor layer, a first electrode and a second electrode. The N-type semiconductor layer is located on the sapphire substrate. The active layer has an active area with a defect density of DD≥2×10 ⁷ /cm ³ , and the active layer is located between the N-type semiconductor layer and the P-type semiconductor layer. The wavelength λ of the light emitted by the active layer satisfies 222nm≤λ≤405nm. The active layer includes an i-layer quantum Lei layer and an (i-1) quantum well layer. Each quantum well layer is located between any two quantum Lei layers, and i is a natural number greater than or equal to 2. In the active layer of one of the light-emitting diodes, N-type impurities are doped in at least k layers in the quantum Lei layer. k is a natural number greater than or equal to 1. When i is an even number, k≥i/2, and when i is an odd number. When, k≥(i-1)/2. The first electrode and the second electrode are respectively located on the N-type semiconductor layer and the P-type semiconductor layer.

Description

led

technical field

The invention relates to a light emitting diode, in particular to a light emitting diode (light emitting diode, LED for short) which can improve luminous efficiency.

Background technique

A light-emitting diode is a semiconductor element, mainly composed of III-V group element compound semiconductor materials. Because this semiconductor material has the characteristic of converting electrical energy into light, when an electric current is applied to this semiconductor material, the electrons inside it will combine with holes, and the excess energy will be released in the form of light to achieve luminescence. Effect.

Generally speaking, due to the mismatch between the lattice constant of gallium nitride used as the material of the epitaxial layer in the light-emitting diode and the lattice constant of the sapphire substrate, the degree of the lattice constant mismatch is about 16%, resulting in A large number of defects are generated at the junction of lattice growth, which leads to a large attenuation of luminous intensity. Although there are inevitably certain defects in the crystal growth process of gallium nitride in light-emitting diodes. However, when the wavelength of the light emitted by the LED is 450nm, since it is known that the lattice stress will be released near the defect to form an indium self-accumulation region, when carriers easily enter the indium self-accumulation region before moving to the defect, forming The so-called localized effect (localized effect). Due to the quantum confinement effect in the self-assembled region of indium, the recombination efficiency of carriers can be improved. Therefore, even though the gallium nitride light-emitting diode has a high defect density in the active region due to the limitation of the crystal growth process, it still has a light wavelength of 450nm. A certain level of luminous efficiency can be maintained.

However, when the light-emitting band of the light-emitting diode gradually shifts from the blue light to the ultraviolet light band, since the indium content in the active layer gradually decreases, the formation area of indium self-agglomeration is relatively reduced, which makes the carriers in the light-emitting diode easy to Moved to the defect to produce non-radiative recombination, resulting in a significant reduction in the luminous efficiency of the light-emitting diode in the near-ultraviolet light; moreover, the nitride semiconductor itself has a polarization field effect that causes the energy band of the active layer to bend, and the electron-hole pair is not easy to be absorbed. Confined in the quantum well layer, it cannot effectively radiatively recombine. In addition, electrons are more likely to overflow (overflow) to the P-type semiconductor layer, resulting in a decrease in luminous intensity. Furthermore, since the mobility of holes is smaller than that of electrons, when holes are injected from the P-type semiconductor layer into the active layer, the Most of the holes are confined in the quantum well layer closest to the P-type semiconductor layer, and it is not easy to distribute uniformly in all the quantum well layers, resulting in a decrease in luminous intensity. Therefore, the industry strives to develop light-emitting diodes with high luminous intensity.

Contents of the invention

The invention proposes a light-emitting diode, which can improve the luminous efficiency of the light-emitting diode in the 222nm-405nm light-emitting wavelength band by making the number of quantum epitaxy layers doped with N-type impurities in the quantum epitaxy layer meet a specific ratio.

The present invention proposes another light-emitting diode, which can improve the luminous efficiency of the light-emitting diode in the 222nm-405nm light-emitting band by making the quantum epitaxy layer doped with N-type impurities closest to the P-type semiconductor have the minimum doping concentration.

The present invention further proposes a light-emitting diode, which can improve the luminous efficiency of the light-emitting diode in the 222nm-405nm light-emitting band by making the doping concentration of the quantum epitaxial layer doped with N-type impurities satisfy a specific relationship.

The invention provides a light emitting diode, which includes a substrate, an N-type semiconductor layer, an active layer, a P-type semiconductor layer, a first electrode and a second electrode. The N-type semiconductor layer is located on the substrate. The active layer has an active region with a defect density of DD, wherein DD≥2×10 ⁷ /cm ³ . Located on a part of the N-type semiconductor layer, the wavelength λ of the light emitted by the active layer satisfies 222nm≤λ≤405nm. The active layer includes the i-layer quantum epitaxy layer and the (i-1) quantum well layer. Each quantum well layer Located between any two quantum epitaxy layers, and i is a natural number greater than or equal to 2, wherein at least k layers of the quantum epitaxy layer are doped with N-type impurities, k is a natural number greater than or equal to 1, when i is an even number, k ≥i/2, when i is an odd number, k≥(i-1)/2. The P-type semiconductor layer is on the active layer. The first electrode is located on a partial area of the N-type semiconductor layer, and the second electrode is located on a partial area of the P semiconductor layer.

The present invention provides another light emitting diode, which includes a substrate, an N-type semiconductor layer, an active layer, a P-type semiconductor layer, a first electrode and a second electrode. The N-type semiconductor layer is located on the substrate. The active layer has an active region with a defect density of DD, wherein DD≥2×10 ⁷ /cm ³ . The active layer is located on a part of the N-type semiconductor layer and the emitted light wavelength λ satisfies 222nm≤λ≤405nm. The active layer includes an i-layer quantum epitaxy layer and an (i-1) quantum well layer. Each quantum well layer Located between any two quantum epitaxy layers, and i is a natural number greater than or equal to 2, wherein at least k layers of the quantum epitaxy layer are doped with N-type impurities, k is a natural number greater than or equal to 1, when i is an even number, k ≥i/2, when i is an odd number, k≥(i-1)/2. The P-type semiconductor layer is located on the active layer, and the doping concentration of the quantum epitaxy layer closest to the P-type semiconductor in the k-layer quantum epitaxy layer is less than or equal to the doping concentration of other quantum epitaxy layers in the k-layer quantum epitaxy layer. The first electrode is located on a partial area of the N-type semiconductor layer, and the second electrode is located on a partial area of the P semiconductor layer.

The present invention further provides a light emitting diode, which includes a substrate, an N-type semiconductor layer, an active layer, a P-type semiconductor layer, a first electrode and a second electrode. The active region has a defect density DD, wherein DD≥2×10 ⁷ /cm ³ . The N-type semiconductor layer is located on the substrate. An active layer, located on a part of the N-type semiconductor layer, the light wavelength λ emitted by the active layer satisfies 222nm≤λ≤405nm, and the active layer includes an i-layer quantum epitaxy layer and an (i-1) quantum well layer , each quantum well layer is located between any two quantum epitaxy layers, and i is a natural number greater than or equal to 2, wherein doping N-type impurities in at least k layers in the quantum epitaxy layer, k is a natural number greater than or equal to 1, when i When it is an even number, k≥i/2, when i is an odd number, k≥(i-1)/2, the doping concentration of the k-layer quantum epitaxy layer is 5×10 ¹⁷ /cm ³ to 1×10 ¹⁹ /cm ³ . The P-type semiconductor layer is on the active layer. The first electrode and a second electrode, wherein the first electrode is located on a partial area of the N-type semiconductor layer, and the second electrode is located on a partial area of the P semiconductor layer.

Based on the above, in the light-emitting diode of the present invention, by making the number of quantum epitaxy layers doped with N-type impurities in the active layer conform to a specific relationship, or by making the quantum epitaxy layers doped with N-type impurities in the active layer The one closest to the P-type semiconductor has the smallest doping concentration, or the doping concentration of the quantum epitaxial layer doped with N-type impurities satisfies a specific relationship, so that the N-type impurities can smooth the influence of defects on carriers and improve luminescence The recombination efficiency of the carriers of the diode, therefore, the light emitting diode of the present invention can greatly improve the luminous efficiency of the light emitting diode at 222nm-405nm by using any of the above technical means.

The present invention proposes a light-emitting diode. Among the three quantum epitaxy layers closest to the P-type semiconductor layer, the thickness of the quantum epitaxy layer closest to the P-type semiconductor layer is greater than the thickness of the other two quantum epitaxy layers, so that electrons can be empty. The hole pairs are evenly distributed in the quantum epitaxial layer of the active layer, thereby improving the luminous intensity of the light-emitting diode in the 222nm-405nm luminous wavelength band.

The present invention proposes another light-emitting diode, which can make electron-hole pairs evenly distributed in the quantum epitaxy layers of the active layer by making the thicknesses of the three quantum epitaxy layers closest to the P-type semiconductor layer conform to a specific relationship, thereby The luminous intensity of the light-emitting diode in the 222nm-405nm luminous band can be improved.

The invention provides a light-emitting diode, which includes a substrate, an N-type semiconductor layer and a P-type semiconductor layer, an active layer, a first electrode, and a second electrode. The N-type semiconductor layer is located between the substrate and the P-type semiconductor layer. The active layer is located between the N-type semiconductor layer and the P-type semiconductor layer. The light wavelength λ emitted by the active layer satisfies 222nm≤λ≤405nm. The active layer includes the i-layer quantum epitaxy layer and the (i-1) layer quantum well Each quantum well layer is located between any two quantum epitaxial layers, and i is a natural number greater than or equal to 2. The thickness of each quantum epitaxial layer in the i layer is T ₁ , T ₂ , T in sequence from the P-type semiconductor side. ₃ . . . T _i , wherein T ₁ is greater than T ₂ and T ₃ or T ₁ >T ₂ =T ₃ . The first electrode is located on a partial area of the N-type semiconductor layer, and the second electrode is located on a partial area of the P semiconductor layer.

The present invention proposes another light emitting diode, which includes a substrate, an N-type semiconductor layer and a P-type semiconductor layer, an active layer, a first electrode, and a second electrode. The N-type semiconductor layer is located between the substrate and the P-type semiconductor layer. The active layer is located between the N-type semiconductor layer and the P-type semiconductor layer. The light wavelength λ emitted by the active layer satisfies 222nm≤λ≤405nm. The active layer includes the i-layer quantum epitaxy layer and the (i-1) layer quantum well Each quantum well layer is located between any two quantum epitaxial layers, and i is a natural number greater than or equal to 2. The thickness of each quantum epitaxial layer in the i layer is T ₁ , T ₂ , T in sequence from the P-type semiconductor side. ₃ ... T _i , wherein the thickness of the i-layer quantum epitaxy layer satisfies: T ₁ =T ₂ >T ₃ or T ₁ >T ₂ >T ₃ . . The first electrode and the second electrode are respectively located on a partial area of the N-type semiconductor layer and a partial area of the P semiconductor layer.

Based on the above, in the light-emitting diode of the present invention, among the three quantum epitaxy layers closest to the P-type semiconductor layer, the thickness of the quantum epitaxy layer closest to the P-type semiconductor layer is greater than the thickness of the remaining two quantum epitaxy layers, or by making the thickness of the quantum epitaxy layer closest to the P-type semiconductor layer The thickness of the quantum epitaxial layer in the source layer conforms to a specific relationship. Through any of the above-mentioned technical means, the uniform distribution of electron-hole pairs in the active layer can be increased, and the recombination probability of electron-hole pairs can be increased. A technical means can greatly increase the luminous intensity of light-emitting diodes at 222nm-405nm.

Description of drawings

1 is a schematic cross-sectional view of a light emitting diode in an embodiment of the present invention;

2A is a schematic cross-sectional view of a single quantum well active layer in a light emitting diode according to an embodiment of the present invention;

2B is a schematic cross-sectional view of a multiple quantum well active layer in a light emitting diode according to an embodiment of the present invention;

3 is an enlarged schematic cross-sectional view of an active layer of a light emitting diode;

Fig. 4 A has shown the comparative example of the light-emitting diode of the present invention;

Figure 4B shows an embodiment of a light emitting diode of the present invention;

FIGS. 5A to 5D respectively show the relational diagrams of the electron concentration of the simulation to the light-emitting diode when the number of doped quantum epitaxy layers in FIG. 3 is changed;

FIGS. 6A to 6D respectively show the relational diagrams of the simulation versus the hole concentration of the light-emitting diode when the number of layers of the doped quantum epitaxy layer in FIG. 3 is changed;

FIGS. 7A to 7D respectively show the relationship diagrams of the simulation to the electron-hole recombination probability of the light-emitting diode when the number of doped quantum epitaxy layers in FIG. 3 is changed;

FIGS. 8A to 8D respectively show the relational diagrams of the simulation to the non-radiative recombination probability of the light-emitting diode when the number of layers of the doped quantum epitaxy layer in FIG. 3 is changed;

FIG. 9A is a graph showing the relationship between the current-light output power curve of different doped layers in the quantum epitaxy layer of the light-emitting diode;

FIG. 9B is a graph showing the relationship between different numbers of doped layers and the current-voltage curve in the quantum epitaxial layer of the light-emitting diode;

10A is a graph showing the relationship between different doping concentrations in the quantum epitaxial layer in the light emitting diode and the current-light output power curve;

FIG. 10B is a graph showing the relationship between different doping concentrations and current-voltage curves in the quantum epitaxial layer of the light emitting diode;

11A to 11C are structural design diagrams of several light-emitting diodes in an embodiment of the present invention;

Fig. 12 is a simulation diagram of the luminous intensity of each light emitting diode in Fig. 11A to Fig. 11C;

FIGS. 13A to 13C respectively represent the electron and hole concentration simulation diagrams of the light-emitting diodes in FIGS. 11A to 11C ;

FIG. 14A and FIG. 14B are energy band simulation diagrams of the light-emitting diodes in FIG. 11B and FIG. 11C respectively;

Fig. 15 is a simulation diagram of electron current density of each light emitting diode in Fig. 11A to Fig. 11C;

Fig. 16 is a graph of light output curve versus injection current in each light emitting diode in Table 2;

Fig. 17 is an embodiment of the light emitting diode of the present invention;

Fig. 18 is another embodiment of the light emitting diode of the present invention;

Fig. 19 is another embodiment of the light emitting diode of the present invention.

[Description of main component symbols]

200, 200A-200I, I-IX: LED

210: Substrate

212: Nitride semiconductor cladding layer

220: N-type semiconductor layer

222: the first N-type doped gallium nitride layer

224: the second N-type doped gallium nitride layer

230: active layer

230A: Single quantum well active layer

230B: multiple quantum well active layer

232, 232a, 232b, 232c, 232d, 232e, 232f: quantum epitaxy layer

234, 234a, 234b, 234c, 234d, 234e: quantum well layer

240: P-type semiconductor layer

242: the first p-type doped gallium nitride layer

244: The second p-type doped gallium nitride layer

250: first electrode

260: second electrode

T ₁ , T ₂ , T ₃ , ..., T _i : the thickness of the quantum epitaxy layer

310: contact layer

320: reflective layer

330: bonding layer

340: Carrier substrate

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view of a light emitting diode in an embodiment of the present invention.

Referring to FIG. 1 , the LED 200 includes a substrate 210 , an N-type semiconductor layer 220 , an active layer 230 , a P-type semiconductor layer 240 , and a first electrode 250 and a second electrode 260 , and the substrate 210 is, for example, a sapphire substrate. Specifically, a nitride semiconductor coating layer 212 (for example, undoped gallium nitride), an N-type semiconductor layer 220, an active layer 230, and a P-type semiconductor layer 240 are sequentially formed on a surface of the sapphire substrate 210. The active layer 230 is located between the N-type semiconductor layer 220 and the P-type semiconductor layer 240, and the N-type semiconductor layer 220 may include the first N-type doped nitride layer sequentially located on the nitride semiconductor cladding layer 212. The gallium layer 222 and the stack of the second N-type doped gallium nitride layer 224, the P-type semiconductor layer 240 may include the first P-type doped gallium nitride layer 242 and the second P-type semiconductor layer on the active layer 230 in sequence. type doped gallium nitride layer 244, wherein between the first n-type doped gallium nitride layer 222 and the second n-type doped gallium nitride layer 224, or between the first p-type doped gallium nitride layer The difference between 242 and the second P-type doped GaN layer 244 may be different thickness or different doping concentration. In addition, the material of the N-type semiconductor layer 220 and the P-type semiconductor layer 240 is, for example, aluminum gallium nitride. Those skilled in the art can select the grown nitride semiconductor cladding layer 212, the first N/P The thickness, doping concentration and aluminum content of the second N/P-type doped GaN layers 222 and 242 and the second N/P-type doped GaN layers 224 and 244 are not limited in the present invention.

Specifically, as shown in FIG. 1 , a nitride semiconductor cladding layer 212 (such as un-doped gallium nitride), a first N-type doped nitride coating layer 212 are sequentially formed on a sapphire substrate 210. The gallium layer 222 and the second N-type doped GaN layer 224, the active layer 230, the first P-type doped AlGaN layer 242 and the second P-type doped GaN layer 244, and respectively The first electrode 250 and the second electrode 260 are formed on the second N-type doped gallium nitride layer 224 and the second type P-type doped gallium nitride layer 244 on partial areas of the surface, so that the first electrode 250 is electrically connected to N type semiconductor layer 220 , and electrically connect the second electrode 260 to the P-type semiconductor layer 240 . Of course, a nitride buffer layer can also be added between the sapphire substrate and the N-type semiconductor, and the present invention is not limited thereto.

The constitution of the active layer 230 is, for example, shown in FIG. 2A and FIG. 2B , which can be a single quantum well active layer 230A or a multiple quantum well active layer 230B. 2A is a schematic cross-sectional view of a single quantum well active layer in a light emitting diode according to an embodiment of the present invention, and FIG. 2B is a schematic cross-sectional view of a multiple quantum well active layer in a light emitting diode according to an embodiment of the present invention. Generally speaking, the active layer includes an i-layer quantum epitaxy layer and (i-1) quantum well layer, and each quantum well layer is sandwiched between any two quantum epitaxy layers, so i is a natural number greater than or equal to 2 . For example, as shown in FIG. 2A, a single quantum well active layer 230A can be composed of two quantum epitaxy layers 232 and a quantum well layer 234 sandwiched therebetween, thus forming a quantum epitaxy layer 232/quantum well layer 234/quantum epitaxy layer 232 . Taking the light-emitting diode 200 in the 222nm-405nm light-emitting band as an example, the material of the quantum well layer 234 is, for example, Al _m In _n Ga _1-mn N, where 0≤m<1, 0≤n≤0.5, m+n≤1, And x>m, n≥y, and the material of the quantum epitaxial layer 232 is, for example, Al _x In _y Ga _1-xy N, where 0≤x≤1, 0≤y≤0.3, and x+y≤1, in the Those skilled in the art can select the content of m and n, or the content of x and y to be grown according to actual requirements such as different light emission bands, and the present invention is not limited thereto.

In addition, the configuration type of the active layer can also be the type of the multiple quantum well active layer 230B shown in FIG. 2B . As shown in FIG. 2B, the multiple quantum well active layer 230B can be composed of at least two pairs of stacked layers of quantum epitaxy layer 232 and quantum well layer 234, such as three pairs of quantum epitaxy layer 232/quantum well layer 234 shown in FIG. 2B Repeated overlays.

It should be noted that, in the light-emitting diode 200 of the present invention, the quantum epitaxy layer 232 is doped with N-type impurities in the active layer 230 to change the number of doped quantum epitaxy layers 232 in the quantum epitaxy layer 232 and the doping concentration. , and different doping concentration distributions in the doped quantum epitaxy layer 232 to improve the luminous efficiency of the light emitting diode 200 in the 222nm-405nm band. Specifically, although there is a certain defect density in the gallium nitride growth technology due to process limitations, even if the active layer 230 in the light emitting diode 200 has a level of 10 ⁷ , by adjusting the doping in the quantum epitaxy layer 232 The number of layers, doping concentration, etc. of the quantum epitaxy layer 232 can be intentionally doped with N-type impurities to reduce the influence of the defect density in the active region on carriers, and effectively improve the luminous efficiency. In particular, it has a significant improvement effect on the light emitted by the active layer 230 with a wavelength ranging from 222 nm to 405 nm.

In the following, experimental results will be used to illustrate the efficacy of the light emitting diode 200 of the present invention proposed by the inventor. In the following embodiments, silicon is used as the N-type impurity as the implementation range, but those skilled in the art can also use other elements in the IVA group of the same family as silicon to replace silicon in the embodiments, or V can be selected. Or replace the silicon in the embodiment with the element of VIA group, such as oxygen, as long as it can replace the aluminum, indium, and gallium element of the IIIA group, and can provide electrons as N-type doping, the present invention can also be realized.

FIG. 3 is an enlarged schematic cross-sectional view of an active layer of a light emitting diode. As shown in FIG. 3 , the active layer 230 of this embodiment includes six quantum epitaxy layers and five quantum well layers, and each quantum well layer is sandwiched between any two quantum epitaxy layers. The quantum epitaxy layers are 232a, 232b, 232c, 232d, 232e, 232f in sequence from the N-type semiconductor side, and the quantum well layers are quantum well layers 234a, 234b, 234c, 234d, 234e.

FIG. 4A shows an optical simulation diagram of a light emitting diode of the present invention as a comparative example, and FIG. 4B shows an optical simulation diagram of a light emitting diode of the present invention, wherein the defect density in FIG. 4A and FIG. 4B is set to 1×10 ⁸ /cm ³ . Please refer to FIG. 4A first. FIG. 4A is a diagram showing the relationship between the number of doped quantum epitaxy layers of the quantum epitaxy layers 232a-232f in the light-emitting diode and the luminous intensity in the band near 450nm. Please refer to FIG. 3 and FIG. 4A at the same time. , the horizontal axis represents the luminous wavelength (unit: nanometer), the vertical axis represents the luminous intensity (unit: au), and the numbers before and after the slash in different line segments A, B, C, and D represent the quantum epitaxy as shown in Figure 3. The layers 232 a - 232 f have the numbers of doped quantum epitaxy layers and undoped quantum epitaxy layers, and the number of doped layers is counted from the side of the N-type semiconductor layer 220 . For example, 6/0 in the line segment A represents that the six layers of quantum epitaxy layers 232a-232f are all doped, and 4/2 in the line segment B represents that the four layers of quantum epitaxy layers 232a-232d near the N-type semiconductor layer 220 are doped with quantum epitaxy layers. The number of layers of the undoped quantum epitaxy layers 232e-232f is two layers, and 2/4 in the line segment C represents that the two-layer quantum epitaxy layers 232a-232b near the side of the N-type semiconductor layer 220 are doped quantum epitaxy layers , and the number of undoped quantum epitaxy layers 232c-232f is four layers, and 0/6 in line segment D represents that all six quantum epitaxy layers 232a-232f are undoped. As shown in FIG. 4A , the results show that increasing the number of doped quantum epitaxy layers reduces the luminous efficiency of the light-emitting diode at a wavelength near 450 nm.

In contrast, when the number of doped quantum epitaxy layers in the quantum epitaxy layer 232 is increased, the luminous intensity of the light emitting diode in the 222nm-405nm band can be effectively increased. In detail, FIG. 4B is a graph showing the relationship between the number of layers of doped quantum epitaxy layers and the luminous intensity of the luminous wavelength near 365nm in the light-emitting diode. The horizontal axis, vertical axis, and line segment in FIG. 4B The definition is similar to that in Fig. 4A, except that Fig. 4B shows that the main peak is in the 222nm-405nm range near 365nm. As shown in FIG. 4B , the results show that increasing the number of doped quantum epitaxy layers 232 helps to improve the luminous efficiency of the light-emitting diode in the 222nm-405nm band.

The inventor deduces based on the aforementioned results in FIG. 4A and FIG. 4B that when the luminous wavelength band emitted by the light-emitting diode is around 450nm, due to the strong localized effect in the quantum well, the carriers are not easily affected by the defect density, so Doping N-type impurities in the quantum epitaxy layer cannot enhance the luminous intensity near 450nm, and excessive doping will cause carrier overflow phenomenon and thus reduce luminous intensity, as shown in FIG. 4A . However, for a light-emitting diode with a light-emitting wavelength around 365nm, the effect of doping the quantum epitaxy layer with N-type impurities is completely opposite to that of a light-emitting diode with a light-emitting wavelength around 450nm.

In detail, as shown in FIG. 4B, when the luminescence band emitted by the light-emitting diode is in the 222nm-405nm luminescence band near the main peak of 365nm, due to the weakening of the local effect of the quantum well, the carrier is affected by the defect density. Doping N-type impurities (such as silicon) in a given quantum epitaxy layer can help compensate the influence of defect density on carriers. In other words, N-type impurities can also provide electrons for radiative recombination, so it can effectively improve luminescence. The luminous efficiency of the diode in the 222nm to 405nm luminous wavelength band. The so-called N-type impurity here is a group IV impurity provided purposefully from the outside as a substitute for group III elements. As shown in Figure 4B, the luminous intensity in the 222nm to 405nm luminescent band increases as the number of doped quantum epitaxy layers increases, especially when the number k of doped quantum epitaxy layers and the total number of quantum epitaxy layers i satisfy the following relationship When the formula is used, the effect of improving the luminous efficiency is remarkable: when i is an even number, k≥i/2; when i is an odd number, k≥(i-1)/2.

In order to further verify the above inference, for light-emitting diodes with light-emitting wavelengths from 222nm to 405nm, Fig. 5A to Fig. 8D are further used to show that when the number of doped quantum epitaxy layers 232 in Fig. The relationship diagram of hole concentration, electron-hole recombination probability, and non-radiative recombination probability, wherein the horizontal axis of Fig. 5 to Fig. 8 represents the distance from the substrate surface (unit: nanometer), and A, B, Figures C and D respectively represent the number of layers of doped quantum epitaxy layer and undoped quantum epitaxy layer, and their definitions are the same as the line segments A to D in Figures 4A and 4B, and will not be repeated here.

It can be seen from the electron concentration simulation diagrams in FIG. 5A to FIG. 5D that when the number of doped quantum epitaxy layers increases, the electron concentration gradually increases. From the hole concentration simulation diagrams in Figure 6A to Figure 6D, it can be seen that when the number of doped quantum epitaxy layers increases, the hole concentration gradually decreases, and the overall hole concentration when all quantum epitaxy layers are not doped Highest. From the simulation diagrams of the electron-hole recombination probability in Figure 7A to Figure 7D, it can be seen that although the overall hole distribution is relatively uniform when the quantum epitaxy layers are all doped, it should be that the light-emitting diode in which all the quantum epitaxy layers are not doped in Figure 7D has a higher Electron-hole recombination probability, however, from the trend of Figure 7A to Figure 7D, the electron-hole recombination probability is the highest when all the quantum epitaxy layers 232 in Figure 7A are doped, but all the quantum epitaxy layers 232 in Figure 7D are not doped The probability of electron-hole recombination is the lowest. Therefore, FIG. 7A to FIG. 7D can also verify the inference that N-type impurities can provide electrons for radiative recombination, thus effectively improving the luminous efficiency of light-emitting diodes in the 222nm-405nm light-emitting wavelength band. Furthermore, from the simulation diagrams of electron-hole non-radiative recombination probability in Figure 8A to Figure 8D, it can be seen that the non-radiative recombination probability is the lowest when all the quantum epitaxy layers in Figure 8A are doped, while all the quantum epitaxy layers in Figure 8D are not doped The probability of electron-hole non-radiative recombination is the highest when it is miscellaneous. Combining the results of Figure 7A to Figure 7D and Figure 8A to Figure 8D, it can be known that doping N-type impurities in the quantum epitaxy layer can provide electrons and increase the probability of electron-hole radiative recombination. , and effectively improve the luminous efficiency, while reducing the non-radiative recombination probability of electron holes in non-luminous forms such as heat, which can also verify the inference that N-type impurities can improve the luminous intensity of light-emitting diodes in the 222nm to 405nm luminescent band.

Table 1 records that when the structure of the active layer in the light-emitting diode is shown in Figure 3, the luminous intensity performance of the light-emitting diode at different currents, and the performance of the forward voltage vary with the difference between the doped quantum epitaxy layer and the undoped quantum epitaxy layer. The number of layers changes. In the experiments in Table 1, the doping concentrations C ₁ , C ₂ , ... C _k of each doped quantum epitaxy layer are, for example, 2×10 ¹⁸ /cm ³ , while in this In the embodiment of the invention whose emission wavelength is 365nm, the material of the quantum well layer is In _c Ga _1-c N, where 0≤c≤0.05, the material of the quantum epitaxy layer is Al _d Ga _1-d N, and d is between 0 and 0.25 Between, in this embodiment, the optimal value of the aluminum content is between 0.09-0.20, the thickness of the quantum epitaxial layer is, for example, 5 nm-15 nm, and in this embodiment, the thickness is preferably 6 nm-11 nm. Moreover, the results of Table 1 are shown in Figure 9A and Figure 9B, wherein Figure 9A shows the relationship between the number of doped layers in the quantum epitaxy layer of the light-emitting diode and the current-light output power curve, and Figure 9B shows the luminescence The relationship between the number of doped layers and the current-voltage curve in the quantum epitaxial layer of the diode.

Table 1

From the results in Table 1 and FIG. 9A , it can be seen that the light output power of the light emitting diodes 200A˜ 200E increases as the number of doped quantum epitaxy layers in the existing quantum epitaxy layers increases. In detail, first of all, when no N-type impurities are doped, its doping concentration is 0, but its GaN material will have its own background doping concentration, and the concentration will vary depending on different epitaxy techniques or different epitaxy qualities. The difference is that in this embodiment, since the background doping concentration cannot be measured, the undoped concentration is represented by N.A. At this time, when none of the six quantum epitaxy layers is doped with N-type impurities (such as silicon) When the light output power is 9.5mW (LED 200A). When two of the six quantum epitaxy layers are doped with N-type impurities (for example, in the quantum epitaxy layers 232a-232f shown in FIG. ), the light output power of the light-emitting diode 200B can be raised to 10.6mW from the undoped 9.5mW, and more preferably, when there are four doped quantum epitaxy layers 232 in the six-layer quantum epitaxy layer 232 (if purposefully Doping the four quantum epitaxial layers 232a-232d closest to the N-type semiconductor 220 in FIG. Therefore, when the layer number k of the doped quantum epitaxy layer 232 is greater than or equal to half of the total layer number i of the quantum epitaxy layer 232, the luminous efficiency of the light emitting diode 200C can be effectively improved. In addition, when five quantum epitaxy layers are doped, the light output power of the light emitting diode 200D is 24.2mW, and when all the quantum epitaxy layers 232 are doped (for example, all six quantum epitaxy layers 232a-232f in FIG. purposeful doping), the light output power of the light emitting diode 200E can be increased to 31.1mW, which is nearly three times as much as the original.

In addition, from the results in Table 1 and FIG. 9B, it can be seen that doping N-type impurities in the quantum epitaxy layer can not only effectively increase the luminous efficiency of the light-emitting diode 200A, but also reduce the resistance value of the quantum epitaxy layer, thereby reducing the light-emitting diode. forward voltage. For example, the forward voltage drops from 4.36V where all quantum epitaxy layers are undoped to 4.14V where all quantum epitaxy layers are doped. The above results indicate that increasing the number of doped layers in the quantum epitaxy layer can compensate the influence of defect density on the luminous efficiency of the light emitting diode in the 222nm-405nm wavelength band (the main peak is around 365nm). In other words, the N-type impurities doped in the quantum epitaxy layer can effectively provide electrons for radiative recombination and reduce the energy release of non-radiative recombination such as heat, so it can effectively improve the luminous efficiency. The above experimental results are verified again The simulation results of the aforementioned Figures 5 to 8 are shown.

Therefore, it can be seen from the above that the light-emitting diode of the present invention can make the number of quantum epitaxy layers doped with N-type impurities in the quantum epitaxy layer of the active layer meet a specific ratio, thereby effectively improving the light-emitting diode in the 222nm-405nm wavelength band. luminous efficiency. Especially when the layer number k of the doped quantum epitaxy layer is greater than or equal to half of the total layer number i of the quantum epitaxy layer, the effect of improving the luminous efficiency is remarkable, specifically, when i is an even number, k≥i/2; when i When it is an odd number, k≥(i-1)/2.

The influence of the doping concentration of N-type impurities in the doped quantum epitaxy layer on the luminous efficiency of the light-emitting diode in the 222nm-405nm band will be further discussed below.

It is recorded in Table 2 that when the structure of the active layer in the light emitting diode is as shown in FIG. The impurity quantum epitaxy layer 232 has four layers, and the other quantum epitaxy layers 232 e - 232 f close to the P-type semiconductor layer are not doped. Table 2 shows the relationship between different doping concentrations in the doped quantum epitaxial layer of the light-emitting diode and the performance of the luminous intensity and the performance of the forward voltage. Moreover, the results of Table 2 are shown in Figure 10A and Figure 10B, wherein Figure 10A shows the relationship between different doping concentrations in the quantum epitaxy layer in the light-emitting diode and the current-light output power curve, and Figure 10B shows the luminescence A plot of different doping concentrations versus current-voltage curves in the quantum epitaxial layer of a diode.

Table 2

From the results of Table 2 and Figure 10A and referring to Figure 3, it can be seen that the light output power of the light-emitting diode increases with the increase of the doping concentration. The background doping concentration, so the undoped concentration is represented by NA, and its light output power is 9.5mW (light-emitting diode 200A); when the doping concentration of the four-layer doped quantum epitaxy layers 232a-232d is 8×10 ¹⁷ cm ^-3 , the light output power of the light emitting diode 200F can be increased from 9.5mW without doping to 11.8mW. Even better, when the doping concentration is 2×10 ¹⁸ cm ^-3 , the light output power of the light emitting diode 200G It can be greatly increased from undoped 9.5mW to double 17.0mW. When the doping concentration is 4×10 ¹⁸ cm ^-3 , the light output power of the LED 200H is 19.1mW, and when the doping concentration When it is 6×10 ¹⁸ cm ^-3 , the light output power of the light emitting diode 200E can be increased to 21.5mW. Therefore, it can be deduced from Table 2 and Figure 10A that when the number of doped layers exceeds half of the total number of layers in the quantum epitaxial layer of the light-emitting diode, and the doping concentration is 5×10 ¹⁷ /cm ³ to 1×10 ¹⁹ /cm 3 cm ³ , the luminous efficiency of the light emitting diodes 200F-200I can be effectively improved.

In addition, from the results in Table 2 and Figure 10B, it can be seen that in the four-layer doped quantum epitaxial layer, when the doping concentration is 5×10 ¹⁷ /cm ³ to 1×10 ¹⁹ /cm ³ , the removal of N-type impurities can improve the luminescence In addition to the luminous efficiency of the diode, the resistance value of the quantum epitaxial layer can be reduced, thereby reducing the forward voltage of the light emitting diode. For example, the forward voltage of a light emitting diode drops from 4.36V with a doping concentration of 0 to 4.09V with a doping concentration of 6×10 ¹⁸ . The above results indicate that increasing the doping concentration of N-type impurities (such as silicon) in the quantum epitaxy layer 232 can effectively compensate the effect of defect density on the luminous efficiency of the light-emitting diode in the 222nm-405nm wavelength band. In other words, the N-type impurities doped in the quantum epitaxy layer can effectively provide electrons for radiative recombination and reduce the energy release of non-radiative recombination, such as heat, so that the luminous efficiency can be effectively improved. The above experimental results are also repeated. The simulation results of the aforementioned Fig. 5 to Fig. 8 are verified.

It is worth mentioning that, according to the above-mentioned embodiments of the light-emitting diodes 200B-200I of the present invention, at least one element from groups IV, V, and VIA can also be selected as an N-type impurity, which can also provide electrons as a result of radiative recombination. Therefore, the luminous efficiency can be effectively improved. In addition, besides the doping concentration in the doped quantum epitaxy layer being equal as shown in Table 1 and Table 2, the doping concentration can also have a gradient change. For example, taking the total number of layers of the quantum epitaxy layer as 6 layers, and the doped quantum epitaxy layer as 4 layers in the 6 layers as an example, the doping concentration of the 4-layer doped quantum epitaxy layer is calculated from the side close to the N-type semiconductor C ₁ , C ₂ , ... C _k in sequence, and C _k ≤ C _k-1 , for example, the doping concentrations of the four doped quantum epitaxy layers 232 a - 232 d are 6×10 ¹⁸ cm ^-3 , 5×10 ¹⁸ cm ^-3 , 4×10 ¹⁸ cm ^-3 , 3×10 ¹⁸ cm ^-3 , in other words, the doping concentration of the doped quantum epitaxy layer changes from the first quantum epitaxy layer near the N-type semiconductor side 232a gradually decreases to the fourth layer 232d closest to the side of the P-type semiconductor, so that the doped N-type impurities can also effectively provide electrons for radiative recombination, thereby effectively improving the luminous efficiency.

Furthermore, the gradient change of the doping concentration C ₁ to C _k in the doped quantum epitaxial layer can also be 6×10 ¹⁸ cm ^-3 , 7×10 ¹⁸ cm ^-3 , 8 ×10 ¹⁸ cm ^-3 , 6×10 ¹⁸ cm ^-3 , in other words, the change in doping concentration can be that the doping concentration of the middle layer number is greater than that of the closest N-type semiconductor and the closest P-type semiconductor. In addition, the gradient change of the doping concentration in the doped quantum epitaxial layer can also be 6×10 ¹⁸ cm ^-3 , 5×10 ¹⁸ cm ^-3 , 8×10 ¹⁸ cm ^-3 from the side close to the N-type semiconductor , 6×10 ¹⁸ cm ^-3 . All in all, as long as the doping concentration of the doped quantum epitaxy layer closest to the P-type semiconductor layer is less than or equal to the doping concentration of other quantum epitaxy layers in the k-doped quantum epitaxy layer, the doped N-type impurity can be effectively Provide electrons for radiative recombination, which can effectively improve the luminous efficiency.

In summary, in the light-emitting diode of the present invention, by making the number of quantum epitaxy layers doped with N-type impurities in the active layer conform to a specific relationship, or by making the quantum epitaxy layer doped with N-type impurities in the active layer The layer closest to the P-type semiconductor has the minimum doping concentration, or the doping concentration of the quantum epitaxial layer doped with N-type impurities satisfies a specific relationship, so that the N-type impurities can smooth the defects of gallium nitride on the carrier. Therefore, the light-emitting diode of the present invention can greatly improve the luminous efficiency of the light-emitting diode in the 222nm-405nm band through any of the above-mentioned technical means.

In addition, the implementation of the light-emitting diode of the present invention is not limited to the above-mentioned manners, and can also be configured with horizontal electrodes or vertical electrodes, both of which can realize the present invention, so it is not limited thereto.

The second embodiment of the present invention also proposes the following light emitting diodes.

11A to 11C are structural diagrams of several light-emitting diodes in an embodiment of the present invention. The horizontal axis represents the position of each quantum epitaxial layer in the stacking position relationship in the light-emitting diode, and the vertical axis represents the energy level diagram of the relative conductive band. The upper part of the quantum epitaxy layer indicates its thickness variation (thickness unit: nanometer).

The light-emitting diode 200A in FIG. 11A shows the structure in which the thicknesses of the quantum epitaxy layers 232a-232f in the light-emitting diode are all the same, and the light-emitting diode 200B in FIG. The structure of the semiconductor layer 220 increases gradually. The LED 200C in FIG. 11C has a structure in which the thickness of the quantum epitaxy layers 232 a - 232 f decreases from the P-type semiconductor layer 240 to the N-type semiconductor layer 220 .

FIG. 12 further shows the simulation diagram of the luminous intensity of each LED in FIG. 11A to FIG. 11C . As shown in FIG. 12 , the light-emitting diode 200C whose thickness of the quantum epitaxy layers 232a-232f decreases gradually from the P-type semiconductor layer 240 to the N-type semiconductor layer 220 has a higher luminous intensity than the light-emitting diode 200A whose quantum epitaxy layers 232a-232f have the same thickness. The light emitting diode 200B whose thickness is higher than the quantum epitaxy layers 232 a - 232 f gradually increases from the P-type semiconductor layer 240 to the N-type semiconductor layer 220 . Among them, the light emitting diode 200B whose luminous intensity gradually increases from the P-type semiconductor layer 240 to the N-type semiconductor layer 220 with the thickness of the quantum epitaxy layers 232 a - 232 f is the weakest.

The mechanism of the influence of the thickness change of the quantum epitaxy layer on the luminous intensity in the light-emitting diodes 200A-200C is further explored.

Figures 13A to 13C respectively show the electron and hole concentration simulation diagrams of the light-emitting diodes in Figures 11A to 11C, and the horizontal axis indicates the position (unit: nanometer) of the film stack from the substrate, where the position at 2060 nanometers is close to the P-type The side of the semiconductor layer 240 , and the position 2000 nm is close to the side of the N-type semiconductor layer 220 , and the thick line and the thin line represent electron concentration and hole concentration (unit: cm ⁻³ ), respectively.

Based on the aforementioned results in FIGS. 11A to 11C , FIG. 12 , and FIGS. 13A to 13C , the inventor deduces that the influence mechanism of the thickness variation of the quantum epitaxy layer on the luminous intensity of the LED is as follows.

Please refer to FIG. 11B and FIG. 13B at the same time. For the electron migration of the light-emitting diode 200B, when the thickness of the quantum epitaxy layers 232a-232f increases from the P-type semiconductor layer 240 to the N-type semiconductor layer 220, due to the migration of electrons from the N-type The quantum epitaxy layers 232a-232f are implanted into the P-type semiconductor layer 220 and migrate to the P-type semiconductor layer 240. Therefore, when the thickness of the quantum epitaxy layers 232a-232f gradually becomes thinner from the N-type semiconductor layer 220 to the P-type semiconductor layer 240, This will make it easier for electrons to move to the P-type semiconductor layer 240 , so that the electron concentration in the quantum well layer 234 a closest to the P-type semiconductor layer 240 is too high.

On the other hand, for the hole migration of the light-emitting diode 200B, as shown in FIG. 13B and FIG. 11B , although the thickness of the quantum epitaxy layer 232a close to the P-type semiconductor layer 240 is relatively thin, the holes are more easily transferred to the N-type semiconductor layer. Layer 220 moves. However, as mentioned above, because there are too many electrons in the quantum well layer 234a closest to the P-type semiconductor layer 240, the electrons overflow phenomenon instead of recombining in the quantum well layer, causing electrons and holes to be ineffective. Radiative recombination occurs, which reduces the concentration of the overall hole injection and reduces the luminous intensity.

On the other hand, please refer to FIG. 11C and FIG. 13C at the same time. For the electron migration of the light-emitting diode 200C, when the thickness of the quantum epitaxy layers 232a-232f increases from the N-type semiconductor layer 220 to the P-type semiconductor layer 240, due to the electron The migration of electrons from the N-type semiconductor layer 220 moves to the P-type semiconductor layer 240 after passing through the quantum epitaxy layers 232a-232f, and the thickness of the quantum epitaxy layer 232 gradually becomes thicker, which can slightly slow down the trend of electrons moving to the P-type semiconductor layer 240, so Firstly, the electron concentration can be uniformly distributed in each quantum well layer 234 a - 234 e of the active layer 230 . In addition, the light-emitting diode 200C has a structure in which the thickness of the quantum epitaxy layers 232a-232f gradually becomes thicker from the N-type semiconductor layer 220 to the P-type semiconductor layer 240, so that the electrons of the light-emitting diode 200C can avoid gathering in the last one like the light-emitting diode 200B. Therefore, the overall electron injection concentration will not be affected by the overflow effect caused by the excess electrons in the last quantum well layer 234a.

On the other hand, for the hole migration of the light-emitting diode 200C, as shown in FIG. 13C and FIG. In the case of the quantum well layer 234a), since the thickness of the quantum epitaxial layers 232a-232f becomes thinner from the P-type semiconductor layer 240 to the N-type semiconductor layer 220, it is beneficial to inject holes into the next quantum well layer 234a-234e. In this way, compared with the LED 200A and the LED 200B, the distribution of hole concentration in the quantum well layer 234 of the LED 200C is more uniform, so that the structure of the LED 200C has an optimal luminous intensity.

FIG. 14A and FIG. 14B are simulation diagrams of energy bands of the light-emitting diodes in FIG. 11B and FIG. 11C respectively, wherein the definition of the horizontal axis is the same as that in FIG. 13A to FIG. 13C . As shown in Figure 14A and Figure 11B, when the thickness of the quantum epitaxial layer 232a closest to the P-type semiconductor layer 240 becomes thinner, its conduction band is lower than the Fermi level indicated by the dotted line, and this phenomenon will make the The quantum well layer 234 a of the P-type semiconductor layer 240 has no confinement effect, and electrons will overflow into the P-type semiconductor layer 240 .

On the other hand, as shown in FIG. 14B and FIG. 11C , the thickness of the quantum epitaxy layer 232a closest to the P-type semiconductor layer 240 of the light emitting diode 200C is relatively thick, so that the conduction band is higher than the Fermi level indicated by the dotted line, which can make the closest The quantum well layer 234 a of the P-type semiconductor layer 240 exerts a proper confinement effect to avoid electron-hole non-radiative recombination from overflowing into the P-type semiconductor layer 240 to reduce the luminous intensity.

FIG. 15 is a simulation diagram of the electron current density of each LED in FIG. 11A to FIG. 11C , wherein the definition of the horizontal axis is the same as that in FIG. 13A to FIG. 13C , and the vertical axis is the electron current density (unit: A/cm ² ). Referring to FIG. 8 , the electron current density of the light emitting diode 200B in the P-type semiconductor layer 240 is higher than that of the light emitting diode 200A and the light emitting diode 200C. This shows that the LED 200B has a current overflow phenomenon.

Table 3 is a simulation diagram of the wave function overlap probability of each quantum well layer 234 .

table 3

Please refer to Table 3 and FIG. 15 at the same time. Since the conduction band of the light-emitting diode 200B is lower than the Fermi level, the quantum well layer 234a closest to the P-type semiconductor layer 240 cannot confine carriers and cause excessive electron overflow to the P-type semiconductor. In the layer 240 , together with FIG. 11B , it can also be verified that the light-emitting diode 200B has excessive electron concentration in the quantum well layer 234 a closest to the P-type semiconductor layer 240 . In addition, as can be seen from FIG. 15 , the electron overflow phenomenon of the light emitting diode 200B is serious, which causes the wave functions of the electron-hole pairs to fail to overlap and thus recombine to emit light.

From the above inferences, it can be seen that when the thickness of the quantum epitaxy layer 232 in the LED 200 changes gradually from the N-type semiconductor layer 220 to the P-type semiconductor layer 240 as in the LED 200B, the light intensity cannot be effectively improved. In contrast, when the thickness of the quantum epitaxial layer 232 in the light-emitting diode 200 changes gradually from the N-type semiconductor layer 220 to the P-type semiconductor layer 240 as in the light-emitting diode 200C, the electron and hole concentrations can be effectively uniformly distributed over the entire quantum In the well layer 234, and at this time, the wave function overlap probability of the electron-hole pair is higher than the wave function overlap probability of the light emitting diode 200A with a uniform thickness of the quantum epitaxy layer 232, so the light emitting diode 200C has the best in this embodiment. light intensity.

It is worth mentioning that, in the quantum epitaxy layer 232 of the active layer 230 , the luminous intensity of the LED 200 is more affected by the thickness variation of the first few quantum epitaxy layers 232 closest to the P-type semiconductor layer 240 . The influence of the thickness variation of the quantum epitaxy layer 232 on the luminous intensity of the light emitting diode 200 in the 222nm-405nm wavelength band will be further discussed below.

Table 4 records that when the structure of the active layer 230 in the light-emitting diode 200 is as shown in Figure 3, when changing the thickness (unit: nanometer) of the quantum epitaxy layers 232a-232f at different positions, it emits light under the current injection of 350mA and 700mA In terms of strength, the thickness of each quantum well layer 234a-234e is 3 nanometers. Moreover, in this embodiment, the material of the quantum well layers 234a-232f is, for example, Inc Ga _{1-c N} , where 0≤c≤0.05, and the material of the quantum epitaxy layers 232a-232f is, for example, AldGa1 _{- d} N, where 0≤d≤0.25, and preferably 0.09≤d≤0.20.

In other words, in this embodiment, there are 6 quantum epitaxy layers 232a-232f in the active layer 230, and its structure can refer to FIG. _{T 1} , _{T 2} , _{T 3 .} 6 as an example) is the thickness of the quantum epitaxy layer 232f closest to the N-type semiconductor side 220.

Table 4

It can be known from Table 4 that the luminous intensity of the light-emitting diode I is 17.0mW under the current injection of 350mA. From the results in Table 4 and with reference to FIG. 3 , it can be seen that among the first three quantum epitaxy layers 232 a to 232 c closest to the P-type semiconductor layer 240 in the light-emitting diode 200 , when the thickness T of the quantum epitaxy layer 232 a close to the P-type semiconductor layer 240 is T ₁ When the thicknesses T2 and T3 of the quantum epitaxy layers 232 b - 232 c closer to the N-type semiconductor layer 220 are greater than T ₂ and T ₃ , that is, when T ₁ is greater than T ₂ and T ₃ , the luminous intensity of the LED can be effectively improved.

Specifically, compared with LED I, the luminous intensity of LED II is greatly reduced to 5.9 mW, because the thickness T1 _of the quantum epitaxy layer 232a of LED II close to the P-type semiconductor layer 240 is relatively thin, and cannot effectively Confining the electrons in the quantum well layer effectively reduces the luminous intensity, which is consistent with the mechanism deduced above.

On the other hand, after light-emitting diode III reduces the thickness T ₃ and T ₄ of the quantum epitaxial layers 232c and 232d in the middle layer of light-emitting diode I, its luminous intensity can be increased to 24.0mW, which means that when the holes are more More quantum well layers 234 a to 234 e are easily implanted into the N-type semiconductor layer 220 . Moreover, like the light-emitting diode IV, after further reducing the thickness of the quantum epitaxy layers 232e and 232f, its light output power is further increased to 30.3mW.

In addition, such as the light emitting diode V, when the thickness T1 _of the quantum epitaxy layers 232a _- 232f is further gradually reduced from the P-type semiconductor layer 240 to the N-type semiconductor layer 220, as shown in Table 4, T1 is gradually reduced to _T6 , The luminous intensity is increased to about twice 33.1mW. In other words, in the light-emitting diode, when the thickness of the _three -layer quantum epitaxy layer 232 closest to the P _- type semiconductor layer 240 satisfies the relationship that T1 is greater _than T2 and T3, the holes can be effectively distributed uniformly in the In the quantum well layer of the source layer 230, the phenomenon of electron overflow can be suppressed, thereby effectively improving the luminous intensity of the light emitting diode.

FIG. 16 is a graph of the light output curve versus the injected current in each light emitting diode in Table 4. FIG. As can be seen from Table 4 and FIG. 16, by adjusting the thickness of the quantum epitaxy layers 232a-232f in the active layer 230, the effect of improving the light output efficiency of the light-emitting diode can be achieved, especially, the closest P For the three quantum epitaxy layers 232 a - 232 c of the type semiconductor layer 240 , by properly adjusting the thicknesses of the three quantum epitaxy layers 232 a - 232 c, the effect of effectively increasing the luminous intensity can be achieved.

Specifically, when the thickness of the quantum epitaxial layer 232 in the i-layer of the active layer 230 satisfies the maximum thickness T ₁ , the effect of increasing the luminous intensity of the light-emitting diode can be achieved.

According to the results of the aforementioned Table 4, it can be seen that the thickness of the quantum epitaxial layer in the middle layer, such as T ₃ and T ₄ , can be thinner than the thickness of the quantum epitaxial layer close to the N-type semiconductor layer 220 and close to the P-type semiconductor layer 240, as shown in the light-emitting diode III. Effectively improve light output efficiency. On the other hand, the thickness of the quantum epitaxy layer 232 close to the N-type semiconductor layer 220 can be smaller than the thickness of the quantum epitaxy layers 232a, 232b close to the P-type semiconductor layer 240, so that the thicknesses of the quantum epitaxy layers 232c-232f are consistent, as if emitting light As shown in diode IV, the light output efficiency can be improved more effectively. Moreover, when the thickness of the quantum epitaxy layer 232 gradually decreases from the P-type semiconductor layer 240 to the N-type semiconductor layer 220 , as shown by the light-emitting diode V, the luminous intensity is the best.

According to the inventor's aforementioned experimental results and inference mechanism, it can be known that the electron-hole pairs can be uniformly distributed in the quantum well layer of the active layer 230, and the confinement effect of the quantum epitaxy layer carriers close to the P-type semiconductor layer 240 can be improved. To effectively improve the luminous efficiency of light-emitting diodes.

Taking the six-layer quantum epitaxy layer 232 in the aforementioned experiment as an example, the thickness T1 of the _first quantum epitaxy layer 232a closest to the P-type semiconductor layer 240 should be the largest, while the thickness T2 of the _second quantum epitaxy layer 232b should be less than or Equal to the thickness T ₁ of the first layer of quantum epitaxy layer 232a, thus the first layer of quantum well layer closest to the P-type semiconductor layer 240 can have a better confinement effect, avoid the overflow effect of electrons, and improve the electron-hole Radiative recombination efficiency.

From the above experiments and inferences, it can be known that by making the thickness T1 of the _first quantum epitaxy layer 232a closest to the P-type semiconductor layer 240 the maximum, the overflow effect of electrons can be effectively avoided, thereby improving the radiation of electron holes. Compound efficiency. Therefore those skilled in the art can infer that when the thickness T ₂ of the second quantum epitaxy layer 232b is equal to the thickness T ₁ of the first quantum epitaxy layer 232a, the first layer closest to the P-type semiconductor layer 240 will be able to At the same time, the quantum well layer exerts a better confinement effect, thereby also avoiding the electron overflow effect and improving the radiation recombination efficiency of electron holes.

Furthermore, the thickness T3 of the _third quantum epitaxial layer 232c should be the thinnest between T1 _- T3, as shown in Table ₄ for light-emitting diodes III-V, which can facilitate hole injection and make Holes are more effectively injected into the quantum well layer 234 on the side of the N-type semiconductor layer 220 , so that the distribution of the holes in the active layer 230 is more uniform. In addition, as shown in LED I in Table 4, when T ₁ >T ₂ =T ₃ , compared with LED II, the light output efficiency can be effectively improved. In addition, as shown in the light-emitting diodes IV and V in Table 4, when the thickness T _i of the quantum epitaxial layer closest to the N-type semiconductor side of T ₆ is the thinnest (i=6 in this embodiment, therefore T ₆ ), The luminous intensity of light-emitting diodes IV and V under 350mA and 700mA current injection is excellent, that is, by making the thickness T _i closest to the N-type semiconductor layer the thinnest in the i-layer quantum epitaxy layer, it can effectively improve light output efficiency.

Further change the number of layers of the quantum well layer and the quantum epitaxy layer in the active layer below, and table 5 is to change the number of layers of the quantum well layer and the quantum epitaxy layer (six layers, nine layers and eleven layers of quantum epitaxy) in the active layer and When changing the thickness (unit: nanometer) of the quantum epitaxy layer at different positions, the performance of the luminous intensity under the current injection of 350mA and 700mA, wherein the thickness of each quantum well layer is 3 nanometers. In other words, in the structure column of Table 5, each number represents the thickness T ₁ ~T _i of each quantum epitaxy layer 232a ~ 232i, and in this column, the numbers from right to left represent the thickness from the P-type semiconductor side. The thicknesses of the quantum epitaxy layers 232 a - 232 i are T ₁ , T ₂ , T ₃ . . . T _i in sequence.

table 5

glow two quantum epitaxy layer Structure (T _i /.../T ₃ /T ₂ /T ₁ ) hair at 350mA hair at 700mA

polar tube brightness brightness I 6 9/9/9/9/9/11 17.0 36.3 V 6 3/3/5/7/9/11 33.1 61.6 VI 9 9/9/9/9/9/9/9/9/11 16.4 35.5 VII 9 2/3/3/5/5/7/7/9/11 24.7 46.8 VIII 11 9/9/9/9/9/9/9/9/9/9/11 11.3 25.4 IX 11 2/2/3/3/3/5/5/7/7/9/11 20.7 39.2

From the results of Table 4 and Table 5, it can be seen that regardless of whether the active layer 230 uses the structure of eight or ten quantum well layers 234 (that is, nine or eleven quantum epitaxy layers 232), when the active layer 230 When the thickness of each quantum epitaxy layer 232 in the i layer satisfies T ₁ >T ₂ ≥T ₃ , especially the design of the quantum epitaxy layer 232 with a gradual thickness can effectively improve the luminous efficiency of the light emitting diode. For example, comparing the structure of the eight-layer quantum well layer 234 of the light-emitting diode VI and the light-emitting diode VII, it can be found that in the structure of the eight-layer quantum well layer 234 of the light-emitting diode VI, the thickness of the quantum epitaxial layer 232 is T ₈ to T ₂ are both set to _9nm , while T1 is set to 11nm. When adjusting the thickness T9 to T1 _of the quantum epitaxy layer 232 in the light-emitting diode VII to be _{2/3/3/5/5/7/7/9/11} nm in sequence, the light output efficiency of the light-emitting diode ( Luminous intensity) is effectively increased from the original 16.4mW to 24.7mW.

On the other hand, comparing the structure of the ten-layer quantum well layer 234 of the light-emitting diode VIII and the light-emitting diode IX, it can be found that the thicknesses _T11 to T2 of the quantum epitaxy layer 232 are all set to ₉ nm, and the thickness of the quantum epitaxy layer 232 is set to T1 is set to _11nm . When the thickness of the quantum epitaxy layer 232 is adjusted to be 2/2/3/3/3/5/5/7/7/9/11 nm in sequence from T ₁₁ to T ₁ , the light emitting diode can be The light output efficiency (luminous intensity) has been effectively increased from the original 11.3mW to 20.7mW.

It is worth mentioning that, in order to further increase the luminous intensity of the light-emitting diode, the inventor proposes that by adjusting the number of layers and doping concentration of the doped quantum epitaxy layer 232 in the quantum epitaxy layer 232, it can be intentionally N-type impurities are doped to reduce the influence of the defect density in the active region on carriers, effectively improving the luminous efficiency, especially for the light emitted by the active layer 230 with a wavelength ranging from 222nm to 405nm.

Especially when the layer number k of the doped quantum epitaxy layer 232 and the total number i of the quantum epitaxy layer 232 satisfy the following relational expression, the effect of improving the luminous efficiency is remarkable: when i is an even number, k≥i/2; when i is an odd number , k≥(i-1)/2. In other words, when the number of doped layers in the quantum epitaxial layer 232 of the light-emitting diode exceeds half of the total number of layers, and the doping concentration is 5×10 ¹⁷ /cm ³ to 1×10 ¹⁹ /cm ³ , it can effectively further Improve the luminous efficiency of light-emitting diodes.

In summary, in the light-emitting diode of the present invention, by making the thickness design of the quantum epitaxial layer in the active layer conform to a specific relationship, holes can be evenly distributed in the quantum well layer, thereby increasing the carrier density of the light-emitting diode. Therefore, the light-emitting diode of the present invention can greatly increase the luminous intensity of the light-emitting diode in the 222nm-405nm band by using any of the above-mentioned technical means.

In addition, the implementation of the light-emitting diode of the present invention is not limited to the above-mentioned types, and can also be configured with horizontal electrodes or vertical electrodes, both of which can realize the present invention, so it is not limited thereto.

Fig. 17 is an embodiment of the light emitting diode of the present invention. As shown in FIG. 17 , the film layers of the light emitting diode 300 include the contact layer 310 from top to bottom; the aforementioned N-type semiconductor layer 220, the active layer 230, the epitaxial layer 270 and the intermediate layer 280, and the P-type semiconductor layer. 240 ; reflective layer 320 ; bonding layer 330 ; and carrier substrate 340 .

Fig. 18 is another embodiment of the light emitting diode of the present invention. As shown in FIG. 18 , the film layers of the light emitting diode 400 include the substrate 210, the nitride semiconductor coating layer 212, the N-type semiconductor layer 220, and the carrier substrate 340 from top to bottom. The carrier substrate 340 is interposed with two stacked layers, as shown on the left side of FIG. and a second stack located on the right of the first stack and at a distance from the first stack, wherein the second stack is mainly composed of a contact layer 310 and a bonding layer 330 . In addition, depending on the requirements of the components, the light emitting diode 400 may place a reflective layer between the contact layer 310 and the bonding layer 330 of the first stack on the right, or set the carrier substrate 340 adjacent to the surface of the second stack on the left, The present invention is not limited thereto.

Fig. 19 is another embodiment of the light emitting diode of the present invention. As shown in FIG. 19 , the film layer structure of the light emitting diode 500 is similar to that in FIG. 18 , except that the light emitting diode 500 in FIG. 19 further omits the substrate 210 above the N-type semiconductor layer 220 compared with the light emitting diode 400 in FIG. 18 . The components of the nitride semiconductor cladding layer 212 and the rest are marked with the same reference numerals as those in FIG. 18 , and will not be repeated here. And, similarly, the light emitting diode 500 can arrange a reflective layer between the contact layer 310 and the bonding layer 330 of the first stacked layer on the right according to the requirements of the device, or arrange the carrier substrate 340 adjacent to the second stacked layer on the left. Apparently, the present invention is not limited thereto.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention, and are not intended to limit the present invention. Within the spirit and principles of the present invention, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (16)

1. A light emitting diode, comprising: a substrate; an N-type semiconductor layer located on the substrate; An active layer having a defect density DD, wherein DD≥2×10 ⁷ /cm ³ , the active layer is located on a part of the N-type semiconductor layer, and the wavelength λ of light emitted by the active layer satisfies 222nm≤λ ≤405nm, the active layer includes i-layer quantum epitaxy layer and (i-1) quantum well layer, each quantum well layer is located between any two quantum epitaxy layers, and i is a natural number greater than or equal to 2, wherein doped Miscellaneous N-type impurities in at least k layers in the quantum epitaxial layer, k is a natural number greater than or equal to 1, when i is an even number, k≥i/2, when i is an odd number, k≥(i-1)/ 2; a P-type semiconductor layer located on the active layer; and A first electrode and a second electrode, wherein the first electrode is located on a partial area of the N-type semiconductor layer, and the second electrode is located on a partial area of the P-type semiconductor layer. 2. The light emitting diode according to claim 1, wherein the k-layer quantum epitaxy layer doped with N-type impurities is located in the k-layer closest to the N-type semiconductor layer among the quantum epitaxy layers. 3. The light emitting diode according to claim 1, wherein the material of the quantum epitaxy layer comprises Al _x In _y Ga _1-xy N, wherein 0≤x≤1, 0≤y≤0.3, and x+y≤1 . 4. The light emitting diode as claimed in claim 1, wherein the thickness of each of the quantum epitaxy layers is between 5 nm and 15 nm. 5. The light emitting diode according to claim 1, wherein the material of the quantum well layer comprises Al _m In _n Ga _1-mn N, wherein 0≤m<1, 0≤n≤0.5, m+n≤1, And x>m, n≥y. 6. A light emitting diode, comprising: a substrate; an N-type semiconductor layer located on the substrate; An active layer having a defect density DD, wherein DD≥2×10 ⁷ /cm ³ , the active layer is located on a part of the N-type semiconductor layer and the emitted light wavelength λ satisfies 222nm≤λ≤405nm, the The active layer includes an i-layer quantum epitaxy layer and an (i-1) quantum well layer, each quantum well layer is located between any two quantum epitaxy layers, and i is a natural number greater than or equal to 2, which is doped with N-type impurities For at least k layers in the quantum epitaxy layer, k is a natural number greater than or equal to 1, when i is an even number, k≥i/2, and when i is an odd number, k≥(i-1)/2; A P-type semiconductor layer is located on the active layer, and the doping concentration of the quantum epitaxy layer closest to the P-type semiconductor in the k-layer quantum epitaxy layer is less than or equal to the doping concentration of other quantum epitaxy layers in the k-layer quantum epitaxy layer impurity concentration; and A first electrode and a second electrode, wherein the first electrode is located on a partial area of the N-type semiconductor layer, and the second electrode is located on a partial area of the P-type semiconductor layer. 7. The light emitting diode according to claim 6, wherein the k-layer quantum epitaxy layer doped with N-type impurities is located in the k-layer closest to the N-type semiconductor layer among the quantum epitaxy layers. 8. The light emitting diode as claimed in claim 7, wherein the doping concentration of the k-layer quantum epitaxy layer is at least 5×10 ¹⁷ /cm ³ . 9. The light-emitting diode according to claim 7, wherein the doping concentration of each quantum epitaxial layer in the k layer is C ₁ , C ₂ , ... C _k in sequence from the N-type semiconductor side, and C _k ≤ C _{k -1} . 10. The light emitting diode according to claim 6, wherein the material of the quantum epitaxy layer comprises Al _x In _y Ga _1-xy N, wherein 0≤x≤1, 0≤y≤0.3, and x+y≤1 . 11. The light emitting diode as claimed in claim 6, wherein the thickness of each of the quantum epitaxy layers is between 5nm and 15nm. 12. The light emitting diode according to claim 6, wherein the material of the quantum well layer comprises Al _m In _n Ga _1-mn N, wherein 0≤m<1, 0≤n≤0.5, m+n≤1, And x>m, n≥y. 13. A light emitting diode comprising: a substrate; an N-type semiconductor layer located on the substrate; An active layer with a defect density of DD, wherein DD≥2×10 ⁷ /cm ³ , the active layer is located on a part of the N-type semiconductor layer, and the wavelength λ of the light emitted by the active layer satisfies 222nm≤ λ≤405nm, the active layer includes an i-layer quantum epitaxy layer and (i-1) quantum well layer, each quantum well layer is located between any two quantum epitaxy layers, and i is a natural number greater than or equal to 2, where Doping N-type impurities in at least k layers of the quantum epitaxy layer, k is a natural number greater than or equal to 1, when i is an even number, k≥i/2, when i is an odd number, k≥(i-1) /2, the doping concentration of the k-layer quantum epitaxial layer is 5×10 ¹⁷ /cm ³ to 1×10 ¹⁹ /cm ³ ; a P-type semiconductor layer located on the active layer; and A first electrode and a second electrode, wherein the first electrode is located on a partial area of the N-type semiconductor layer, and the second electrode is located on a partial area of the P-type semiconductor layer. 14. The light emitting diode according to claim 13, wherein the k-layer quantum epitaxy layer doped with N-type impurities is located in the k-layer closest to the N-type semiconductor layer among the quantum epitaxy layers. 15. The light-emitting diode as claimed in claim 13, wherein the doping concentration of the quantum epitaxy layer closest to the P-type semiconductor in each quantum epitaxy layer in the k-layer is less than or equal to that of other quantum epitaxy layers in the k-layer quantum epitaxy layer doping concentration. 16. The light emitting diode as claimed in claim 13, wherein the thickness of each of the quantum epitaxy layers is between 5nm and 15nm.