KR101018132B1 - Nitride semiconductor light emitting device for polarization alleviation - Google Patents

Abstract

A nitride semiconductor light emitting device for alleviating polarization generated in an active layer.

The nitride semiconductor light emitting device according to the present invention includes an active layer in which a plurality of quantum barrier layers and quantum well layers are alternately stacked between an n-type nitride layer and a p-type nitride layer, and at least one of the quantum barrier layers has a predetermined indium content. A first quantum barrier layer formed of Al _x1 Ga _1-x1-y1 In _y1 N having an aluminum content of 0 <x1 ≦ 1, 0 <y1 ≦ 1, 0 <x1 + y1 ≦ 1); And at least one second quantum barrier layer formed of Al _x2 Ga _1-x2-y2 In _y2 N (0 ≦ x2 <x1, 0 ≦ y2 <y1) on an upper surface or a lower surface of the first quantum barrier layer. do.

According to the present invention, a first quantum barrier layer having an optimal Al content ratio in accordance with the In content ratio is formed in the quantum barrier layer, thereby mitigating stress and polarization in the active layer, maximizing internal quantum efficiency, and thus high-efficiency nitride semiconductor. A light emitting device can be provided.

Quantum barrier layer, quaternary nitride layer, polarization relaxation

Description

Nitride semiconductor light emitting device for reducing polarization

The present invention relates to a nitride semiconductor light emitting device, and more particularly to a nitride semiconductor light emitting device for reducing the polarization generated in the active layer.

Conventional nitride semiconductor devices include, for example, GaN-based nitride semiconductor devices, which are high-speed switching and high-output devices such as blue / green LED light emitting devices, MESFETs and HEMTs, etc. It is applied to the back. In particular, blue / green LED light emitting devices have already been mass-produced and global sales are increasing exponentially.

In particular, in the field of light emitting devices such as light emitting diodes and semiconductor laser diodes among the applications of GaN nitride semiconductors, a semiconductor light emitting device having a crystal layer doped with Group 2 elements such as magnesium and zinc at the Ga position of a GaN nitride semiconductor It is attracting attention as an element emitting blue light.

Such a conventional GaN-based nitride semiconductor light emitting device may be a nitride semiconductor light emitting device having a multi-quantum well structure as shown in Figure 1a, the conventional nitride semiconductor light emitting device 10 is a sapphire substrate 11, An n-type nitride layer 12, an active layer 15 having a multi-quantum well structure, and a p-type nitride layer 17 are included. The transparent electrode layer 18 and the p-side electrode 19b are sequentially formed on the mesa-etched p-nitride semiconductor layer 17, and the n-side electrode 19a is formed on the exposed top surface of the n-type nitride semiconductor layer 12. It is formed in turn.

In general, the active layer 15 is formed of a multi-quantum well structure in which GaN quantum barrier layers 15a and InGaN quantum well layers 15b are alternately stacked, as shown in FIGS. 1A and 1B, and GaN quantum barrier layers. 15A and InGaN quantum well layer 15b have a height of conduction band E _C and a valence band E _V as shown in FIG. 1B. Constant within.

However, stress and strain occur in the quantum barrier layer 15a and the quantum well layer 15b of the active layer 15 due to the difference in lattice constant and thermal expansion coefficient. In particular, when polarization occurs in the active layer, the peak of the wave function A, which indicates the distribution of electrons, appears to be shifted toward the p-nitride semiconductor layer 17 at the center. The wave function B of appears to be biased by the n-type nitride layer 12. As the wave function (A) of the electron and the wave function (B) of the hole are located opposite to each other in the quantum well layer 15b, the light emission recombination efficiency of the electron and the hole is proportional to the overlapping area where the two wave functions overlap. Due to this characteristic, the light emission recombination efficiency of electrons and holes is reduced, and the light emission amount is also reduced.

As described above, electrons and holes that do not recombine cross the quantum barrier and electrons leak toward the p-side electrode 19b, and holes leak toward the n-side electrode 19a. Phosphorus, one of the problems that the luminous efficiency decreases at high current as the current density increases. Therefore, the elimination of the polarization phenomenon due to the difference between the lattice constant and the coefficient of thermal expansion becomes an essential requirement for manufacturing a high output high efficiency light emitting device.

An object of the present invention is to provide a quantum barrier layer and a quantum well layer for mitigating polarization generated in the active layer to provide a nitride semiconductor light emitting device having high output and high efficiency.

Embodiments of the present invention for achieving the above object includes an active layer in which a plurality of quantum barrier layers and quantum well layers are alternately stacked between an n-type nitride layer and a p-type nitride layer, at least one of the quantum barrier layers A first quantum barrier layer formed of Al _x1 Ga _1-x1-y1 In _y1 N (0 <x1 ≦ 1, 0 <y1 ≦ 1, 0 <x1 + y1 ≦ 1) having a predetermined indium content and aluminum content; And at least one second quantum barrier layer formed of Al _x2 Ga _1-x2-y2 In _y2 N (0 ≦ x2 <x1, 0 ≦ y2 <y1) on an upper surface or a lower surface of the first quantum barrier layer. The present invention relates to a nitride semiconductor light emitting device.

In the embodiment of the present invention, the first quantum barrier layer is characterized in that the content ratio (y1) of In is 0 <y1 <0.25 and the content ratio (x1) of Al is 0 <x1 <0.48.

In an embodiment of the present invention, the second quantum barrier layer may include a first nitride layer formed of GaN on a lower surface of the first quantum barrier layer; And a second nitride layer formed of GaN on an upper surface of the first quantum barrier layer.

In an embodiment of the present invention, the first quantum barrier layer has a thickness of 1 nm to 20 nm, the second quantum barrier layer has a thickness of 1 nm to 10 nm, and includes a first quantum barrier layer. The layer is characterized by having a thickness of 3 nm to 30 nm.

In an embodiment of the present invention, the quantum well layer is characterized in that the layer consisting of In _x Ga _{1 - x} N (0 <x ≤ 1).

In an embodiment of the present invention, the first quantum barrier layer and the second quantum barrier layer are characterized in that they have the same energy band.

As described above, the present invention forms a first quantum barrier layer having an optimal Al content ratio in accordance with the In content ratio in the quantum barrier layer, thereby relieving stress and polarization in the active layer, maximizing internal quantum efficiency, The nitride semiconductor light emitting device can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view illustrating a nitride semiconductor light emitting device according to an embodiment of the present invention, and FIG. 3 is an energy band diagram of a portion of an active layer of the nitride semiconductor light emitting device shown in FIG. 2.

As shown in FIG. 2, the nitride semiconductor light emitting device 100 according to the embodiment of the present invention includes a substrate 110, an n-type nitride layer 120, an active layer 150 having a multi-quantum well structure, and a p-type nitride. A transparent electrode layer 180 and a p-side photoelectrode 190b are formed on an upper surface of the mesa-etched p-type nitride semiconductor layer 170 including the layer 170, and an exposed upper surface of the n-type nitride semiconductor layer 120. The n-side electrode 190a is formed in turn. Here, the nitride semiconductor light emitting device 100 according to the embodiment of the present invention forms a buffer layer (not shown) such as AlN / GaN to eliminate the lattice mismatch between the substrate 110 and the n-type nitride layer 120. It can be provided by.

The active layer 150 is formed of a multi-quantum well structure in which a plurality of quantum well layers 150a and quantum barrier layers 150b are alternately stacked, and a part of the quantum barrier layers 150b includes Al first quantum barrier layers. (150b2), i.e., first and second GaN-based materials on both upper and lower sides based on Al _x1 Ga _1-x1-y1 In _y1 N (0 <x1 ≤ 1, 0 <y1 ≤ 1, 0 <x1 + y1 ≤ 1) The second gallium nitride layers 150b1 and 150b3 are formed as second quantum barrier layers to suppress spontaneous polarization due to stress and deformation.

Specifically, one of the quantum barrier layers 150b is Al _x1 Ga _1-x1-y1 In _y1 N (0 <x1 ≤ 1, 0 <y1 ≤ 1, 0 to alleviate polarization occurring in the active layer 150). A first quantum barrier layer 150b2 made of <x1 + y1 ≦ 1) is employed to have a thickness of 1 nm to 20 nm, and a quantum well layer 150a made of In _x Ga _1-x N (0 <x ≤ 1). Al _x2 Ga _1-x2-y2 In _y2 N (0 ≤ x2 <x1, 0 ≤ y2 <y1), for example, GaN without Al or In The first and second gallium nitrides 150b1 and 150b3 made of the material may be formed on the upper and lower surfaces of the first quantum barrier layer 150b2 in a thickness of 1 nm to 10 nm. Here, the upper and lower surfaces of the first quantum barrier layer 150b2 without implementing the first and second gallium nitride layers 150b1 and 150b3 of GaN-based materials on upper and lower surfaces of the first quantum barrier layer 150b2. It may be formed only on one surface, and the quantum barrier layer 150b including the first quantum barrier layer 150b2 may have a thickness of 3 nm to 30 nm.

The reason why the first quantum barrier layer 150b2 composed of Al _x1 Ga _1-x1-y1 In _y1 N is adopted is that AlN having a lattice constant of 3.11, and a lattice constant of 3.19 Å as shown in FIG. 3. Between GaN and InN having a lattice constant of 3.54 Å, the quantum barrier layer 150b has a lattice with the quantum well layer 150a of In _x Ga _1-x N while having an energy band gap of GaN, which is conventionally a quantum barrier layer. In order to solve the mismatch, a point B having a lattice constant difference of "A" may be determined as a characteristic point of the quantum barrier layer 150b, and the first quantum barrier layer satisfying the characteristic point B may be determined. Al _x1 Ga _1-x1-y1 In _y1 N may be applied as the quaternary nitride to prevent stress generation due to the lattice constant difference of the quantum well layer 150a of In _x Ga _1-x N.

In addition, as illustrated in FIG. 4, the first quantum barrier layer 150b2 of Al _x1 Ga _1-x1-y1 In _y1 N is polarized when the In content ratio y1 is 0.2 (III). It can be seen that the Al content ratio (x) has a range of 0 <x1 <0.48 for the boundary graph (I) of the graph and the graph (II) showing the energy band gap of the conventional quantum barrier layer GaN. The first quantum barrier layer 150b2 of Al _x1 Ga _1-x1-y1 In _y1 N having an Al content ratio (x) is formed of the gallium nitride layers 150b1 and 150b3 made of GaN-based materials on both sides of the top and bottom surfaces. Including the quantum barrier layer, polarization generated by the energy band of GaN, which is a conventional quantum barrier layer, can be alleviated. Here, both the first quantum barrier layer 150b2 and the gallium nitride layers 150b1 and 150b3 may be formed to have the same energy band as that of GaN, which is a conventional quantum barrier layer.

Therefore, in the active layer 150 of the multi-quantum well structure in which the quantum barrier layer 150b and the quantum well layer 150a are alternately stacked according to an embodiment of the present invention, the In content ratio y1 is 0 <y1 <0.25 Al _x1 Ga _1-x1-y1 In _y1 N having a content ratio (x1) of Al and an Al content ratio (x1) of 0 <x <0.48 Al _x2 Ga _1-x2-y2 In _y2 A quantum barrier layer 150b including gallium nitride layers 150b1 and 150b3 made of GaN as N and a quantum well layer 150a of In _x Ga _1-x N are alternately formed to form a quantum well layer 150a and a quantum well layer 150a. By mitigating the stress caused by the lattice constant difference between the barrier layers 150b and mitigating the generated polarization, for example, the luminous efficiency of the nitride semiconductor light emitting device that emits blue light can be improved.

Hereinafter, a method of manufacturing the nitride semiconductor light emitting device according to the embodiment of the present invention will be described in detail. Here, in the case where it is determined that the detailed description of the related known structure or function of the nitride semiconductor light emitting device may obscure the gist of the present invention, the detailed description thereof will be omitted.

As shown in FIG. 2, in order to manufacture the nitride semiconductor light emitting device 100 according to the exemplary embodiment of the present invention, an n-type nitride layer 120 is first grown on the substrate 110.

For the growth of the n-type nitride layer 120, for example, silane gas containing n-type dopants such as NH ₃ , trimetalgallium (TMG), and Si is supplied to n- to a predetermined thickness on the substrate 110. The GaN layer is grown to the n-type nitride layer 120. Here, a buffer layer such as AlN / GaN (not shown) may be formed between the substrate 110 and the n-type nitride layer 120 to eliminate lattice mismatch.

After the n-type nitride layer 120 is formed, the active layer 150 is grown on the n-type nitride layer 120. Here, the active layer 150 is formed of a multi-quantum well structure in which a plurality of quantum well layers 150a and quantum barrier layers 150b are alternately stacked, and a part of the quantum barrier layers 150b is Al _x1 Ga _1-x1-. Gallium nitride layers 150b1 and 150b3 made of Al _x2 Ga _1-x2-y2 In _y2 N GaN-based materials on both surfaces of the first quantum barrier layer 150b2 having _y1 In _y1 N and the first quantum barrier layer 150b2. And a second quantum barrier layer, and the quantum well layer 150a is formed of, for example, In _x Ga _1-x N to suppress spontaneous polarization due to stress and deformation.

Specifically, in order to form the quantum well layer 150a made of InGaN on the top surface of the n-type nitride layer 120 to form the active layer 150, nitrogen is used as a carrier gas at a growth temperature of 780 ° C. By supplying NH ₃ , TMG, and trimethylindium (TMI), the quantum well layer 150a made of InGaN can be grown to a thickness of 30 to 100 kPa.

After forming the quantum well layer 150a on the upper surface of the n-type nitride layer 120, the first gallium nitride layer made of Al _x2 Ga _1-x2-y2 In _y2 N on the upper surface of the quantum well layer 150a It can be formed by growing (150b1) to a thickness of 1nm to 10nm.

After the first gallium nitride layer 150b1 is formed, a first quantum barrier layer 150b2 of Al _x1 Ga _1-x1-y1 In _y1 N is formed, and predetermined growth is performed by a metal organic chemical vapor deposition (MOCVD) method. First quantum barrier layer 150b2 consisting of Al _x1 Ga _1-x1-y1 In _y1 N by supplying NH ₃ , TMG, trimethylaluminum (TMA) and trimethylindium (TMI) using nitrogen as a carrier gas at a temperature To form. Here, the first quantum barrier layer 150b2 may be formed of Al _x1 Ga _1-x1-y1 In _y1 N having an In content ratio (y) of 0 <y1 <0.25 and an Al content ratio (x1) of 0 <x1 <0.48 It can be formed from a layer grown with quaternary nitrides.

After forming the first quantum barrier layer (150b2) of Al _x1 Ga _1-x1-y1 In _y1 N, Al _x2 on the upper surface of the first quantum barrier layer (150b2) and the same as the first gallium nitride layer (150b1) The second gallium nitride layer 150b3 formed of Ga _1-x2-y2 In _y2 N may be formed by growing to a thickness of 1 nm to 10 nm.

Thereafter, as described above, the quantum well layer 150a made of InGaN may be grown on the upper surface of the formed second gallium nitride layer 150b3, and the quantum well layer 150a and the quantum barrier layer 150b may be formed. It is possible to form the active layer 150 having a multi-quantum well structure stacked in plurality in turn.

After the active layer 150 is formed as described above, the p-type nitride layer 170 is formed and etched on the active layer 150 in the same manner as the general nitride semiconductor light emitting device, and then the upper surface of the etched p-type nitride semiconductor layer 170 is formed. The transparent electrode layer 180 and the p-side X electrode 190b are formed, and the n-side electrode 190a may be sequentially formed on the exposed n-type nitride semiconductor layer 120.

Therefore, in the present invention, based on the boundary graph (I) of polarization generation shown in FIG. 4 and the graph (II) showing the energy band gap of GaN, which is a conventional quantum barrier layer, By setting the optimum content ratio (x1) of Al, a first quantum barrier layer 150b2 made of ternary nitride of In _x Al _y Ga _1-xy N is formed in the quantum barrier layer 150b, whereby the active layer 150 By reducing stress and polarization inside the circuit and maximizing the internal quantum efficiency, a nitride semiconductor light emitting device having high efficiency can be realized.

Although the technical spirit of the present invention has been described in detail according to the above-described preferred embodiment, it should be noted that the above-described embodiments are for the purpose of description and not of limitation.

In addition, those skilled in the art will understand that various implementations are possible within the scope of the technical idea of the present invention.

1A is a cross-sectional view showing a conventional nitride semiconductor light emitting device.

FIG. 1B is an energy band diagram of a portion of an active layer of the nitride semiconductor light emitting device shown in FIG. 1A; FIG.

2 is a cross-sectional view showing a nitride semiconductor light emitting device according to an embodiment of the present invention.

Figure 3 is a graph of the lattice constant and energy bandgap for explaining the lattice constant of the quaternary nitride of the quantum barrier layer according to an embodiment of the present invention.

Figure 4 is a graph of the indium content ratio and aluminum content ratio of the quaternary nitride of the quantum barrier layer according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100 nitride semiconductor light emitting device 110 substrate

120: n-type nitride layer 150: active layer

150a: quantum well layer 150b: quantum barrier layer

150b1: first nitride layer 150b2: first quantum barrier layer

150b3: second nitride layer 170: p-type nitride layer

180: transparent electrode layer 190a: n-side electrode

190b: p-side electrode

Claims (8)

an active layer in which a plurality of quantum barrier layers and quantum well layers are alternately stacked between an n-type nitride layer and a p-type nitride layer, At least one of the quantum barrier layer A first quantum barrier layer formed of Al _x1 Ga _1-x1-y1 In _y1 N (0 <x1 ≦ 1, 0 <y1 ≦ 1, 0 <x1 + y1 ≦ 1) having a predetermined indium content and aluminum content; And At least one second quantum barrier layer formed of Al _x2 Ga _1-x2-y2 In _y2 N (0 ≤ x2 <x1, 0 ≤ y2 <y1) on the top or bottom surface of the first quantum barrier layer , The first quantum barrier layer and the second quantum barrier layer have the same energy band, but have a different composition, The second quantum barrier layer includes a first nitride layer formed of GaN on a lower surface of the first quantum barrier layer, and a second nitride layer formed of GaN on an upper surface of the first quantum barrier layer. A nitride semiconductor light emitting device. The method of claim 1, The first quantum barrier layer is a nitride semiconductor light emitting device, characterized in that the In content ratio (y1) is 0 <y1 <0.25, Al content ratio (x1) is 0 <x1 <0.48. delete The method of claim 1, The first quantum barrier layer is a nitride semiconductor light emitting device, characterized in that having a thickness of 1 nm ~ 20 nm. The method of claim 1, The second quantum barrier layer A nitride semiconductor light emitting device having a thickness of 1 nm to 10 nm. The method of claim 1, The quantum barrier layer including the first quantum barrier layer is A nitride semiconductor light emitting device having a thickness of 3 nm to 30 nm. The method of claim 1, The quantum well layer is a nitride semiconductor light emitting device, characterized in that the layer consisting of In _x Ga _{1 - x} N (0 <x ≤ 1). delete

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