CN100420045C - Gallium nitride series light-emitting diode - Google Patents

Abstract

The present invention relates to a gallium nitride-based light-emitting diode. The main difference between its structure and the existing gallium nitride-based light-emitting diode is that a thin layer located on a p-type contact layer is formed by using one of silicon nitride (SiN), a short period superlattice structure formed by silicon nitride and undoped indium gallium nitride (InGaN), and a short period superlattice structure formed by silicon nitride and undoped aluminum indium gallium nitride (AlGaInN). On the thin layer, due to the growth of its silicon nitride material, the surface of the gallium nitride-based light-emitting diode is slightly roughened. In this way, the gallium nitride-based light-emitting diode can be prevented from having a higher refractive index than air, resulting in total internal reflection, thereby improving the external quantum efficiency and luminous efficiency of the gallium nitride-based light-emitting diode.

Description

Gallium Nitride Light Emitting Diodes

technical field

The invention relates to a gallium nitride-based light-emitting diode, in particular to a high-brightness gallium nitride-based light-emitting diode with a Micro-roughened surface.

Background technique

Gallium Nitride (GaN)-based light-emitting diodes can produce light-emitting diodes of various colors by controlling the composition of materials, so its related technologies have become the focus of active research and development in the industry and academia in recent years. One of the research focuses of GaN-based light-emitting diodes in academia and industry is to understand the light-emitting characteristics of GaN-based light-emitting diodes, and then propose methods to improve their luminous efficiency and brightness. This high-efficiency and high-brightness gallium nitride-based light-emitting diode will be effectively used in outdoor display boards, automotive lighting and other fields in the future.

The luminous efficiency of gallium nitride-based light-emitting diodes is mainly related to the internal quantum efficiency (Internal Quantum Efficiency) and external quantum efficiency (External Quantum Efficiency) of gallium nitride-based light-emitting diodes. The former is related to the probability of the combination of electrons and holes in the active layer of GaN-based light-emitting diodes to release photons. The easier it is for electron holes to recombine, the easier it is for photons to be generated, the higher the internal quantum efficiency, and the higher the luminous efficiency of gallium nitride-based light-emitting diodes. The latter is related to the probability that photons are not absorbed and affected by the GaN-based light-emitting diode itself, and successfully escape from the GaN-based light-emitting diode. The more photons that can be released out of the GaN-based LED, the higher the external quantum efficiency, and the luminous efficiency of the GaN-based LED is generally higher.

The external quantum efficiency of GaN-based light-emitting diodes mainly depends on the structure and refractive index of the top surface layer. The refractive indices of existing gallium nitride-based light-emitting diodes and air are 2.5 and 1, respectively. Because the existing gallium nitride-based light-emitting diodes have a relatively high refractive index, it is easy to form internal total reflection. The generated photons are not easily released outside the GaN-based light-emitting diode due to internal total reflection, so the external quantum efficiency of the GaN-based light-emitting diode is usually considerably limited.

Contents of the invention

The purpose of the present invention is to provide a gallium nitride-based light-emitting diode, which can actually solve the limitations and defects in the aforementioned related art.

In order to achieve the above object, the present invention provides a gallium nitride-based light-emitting diode, which includes:

Substrates made of alumina single crystal, 6H-SiC, 4H-SiC, Si, ZnO, GaAs, spinel (MgAl ₂ O ₄ ) and single crystal oxides with lattice constants close to those of nitride semiconductors ;

a buffer layer, located on one side of the substrate, made of aluminum gallium indium nitride (Al _a Ga _b In _1-ab N, 0≤a, b<1, a+b≤1) with a specific composition;

an n-type contact layer, located on the buffer layer, is made of gallium nitride-based materials;

an active layer, which is located on the n-type contact layer and covers part of the upper surface of the n-type contact layer, and is made of indium gallium nitride;

a negative electrode on the upper surface of the n-type contact layer not covered by the active layer;

a p-type cladding layer, located on the active layer, made of p-type GaN-based material;

a p-type contact layer, located on the p-type cladding layer, made of p-type gallium nitride;

Micro-roughened thin layer, which is located on the p-type contact layer, a short-period superlattice structure composed of silicon nitride (SiN), silicon nitride and undoped indium gallium nitride (InGaN), and nitride A short-period superlattice structure composed of silicon and undoped aluminum indium gallium nitride (AlGaInN) is composed of one of three materials;

The transparent conductive layer is a metal conductive layer or a transparent oxide layer that is located on the micro-roughened thin layer and covers part of its surface. The metal conductive layer is made of Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy , Pd/Au alloy, Pt/Au alloy, Cr/Au alloy, Ni/Au/Be alloy, Ni/Cr/Au alloy, Ni/Pt/Au alloy, Ni/Pd/Au alloy, The transparent oxide layer is made of ITO, CTO, ZnO:Al, ZnGa ₂ O ₄ , SnO ₂ :Sb, Ga ₂ O ₃ :Sn, AgInO ₂ :Sn, In ₂ O ₃ :Zn, CuAlO ₂ , LaCuOS, NiO, Composed of one of CuGaO ₂ and SrCu ₂ O ₂ ; and

The positive electrode, which is located on the surface of the micro-roughened thin layer not covered by the transparent conductive layer, is made of Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy, Ni/Co alloy, Pd/Au alloy, One of Pt/Au alloy, Ti/Au alloy, Cr/Au alloy, Sn/Au alloy, Ta/Au alloy, TiN, TiWN _x (x≥0), WSi _y (y≥0).

The main difference between the GaN-based light-emitting diode proposed by the present invention and the existing GaN-based light-emitting diode is that it uses silicon nitride (SiN), silicon nitride and undoped InGaN One of the short period (Short Period) superlattice (Superlattice) structure formed by (InGaN) and the short period superlattice structure formed by silicon nitride and undoped aluminum indium gallium nitride (AlGaInN), forming A thin layer on the p-type contact layer. On the thin layer, due to the growth of the silicon nitride material, the surface of the gallium nitride-based light-emitting diode is slightly roughened. In this way, the internal total reflection caused by the higher refractive index of the GaN-based light-emitting diodes than air can be avoided, thereby improving the external quantum efficiency and luminous efficiency of the GaN-based light-emitting diodes.

Fig. 1 is a diagram of brightness data of GaN-based light-emitting diodes produced under different injection currents in the prior art and according to the present invention. As shown in Figure 1, GaN-based light-emitting diodes have the aforementioned short-period superlattice thin layer formed by silicon nitride and undoped indium gallium nitride (In _0.2 Ga _0.8 N), which is significantly larger than Existing gallium nitride-based light-emitting diodes have better luminous efficiency.

In addition to the above-mentioned advantages, due to the low energy gap characteristics of the material forming the thin layer, the metal electrode of the gallium nitride-based light-emitting diode and the resistance between the transparent conductive layer and the thin layer can also be made better than the existing gallium nitride-based light-emitting diodes. The resistance between the first two of the diode and the p-type contact layer is lower, so it is also easier to form an ohmic contact.

Description of drawings

The present invention will be described in more detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the luminance data graph of the existing gallium nitride-based light-emitting diodes manufactured according to the present invention under different injection currents;

2 is a schematic diagram of Embodiment 1 of the gallium nitride-based light-emitting diode of the present invention;

3 is a schematic diagram of Embodiment 2 of the gallium nitride-based light-emitting diode of the present invention;

FIG. 4 is a schematic view of Embodiment 3 of the gallium nitride-based light-emitting diode of the present invention.

Detailed ways

Example 1

FIG. 2 is a schematic view of Embodiment 1 of the gallium nitride-based light-emitting diode of the present invention. As shown in Figure 2, this embodiment 1 uses C-Plane or R-Plane or A-Plane alumina single crystal (Sapphire) or silicon carbide (6H-SiC or 4H-SiC) as the substrate 10, other can be used for The material of the substrate 10 also includes Si, ZnO, GaAs or spinel (MgAl ₂ O ₄ ), or a single crystal oxide whose lattice constant is close to that of nitride semiconductor. Then, a buffer layer composed of aluminum gallium indium nitride (Al _a Ga _b In _1-ab N, 0≤a, b<1, a+b≤1) having a specific composition is formed on one side surface of the substrate 10 20, and the n-type contact layer 30 on the buffer layer 20, the n-type contact layer 30 is made of gallium nitride (GaN)-based material. Next, an active layer 40 is formed on the n-type contact layer 30 , the active layer 40 is made of InGaN and covers part of the upper surface of the n-type contact layer 30 . A negative electrode 42 is additionally formed on the part of the upper surface of the n-type contact layer 30 not covered by the active layer 40 .

之间、成长温度介于600℃～1100℃之间。In Example 1, a p-type cladding layer 50 is formed next on the active layer 40 . The p-type cladding layer 50 is made of GaN-based material. On the p-type cladding layer 50 is a p-type contact layer 60 made of p-type gallium nitride. On the p-type contact layer 60 is the micro-roughened thin layer 70 which is the focus of the present invention. In this embodiment 1, the micro-roughened thin layer 70 is made of silicon nitride (Si _{d Ne} , 0<d, e<1), and its thickness is between 2 ~50

The growth temperature is between 600°C and 1100°C.

On the micro-roughened thin layer 70 , the embodiment 1 further forms a positive electrode 80 and a transparent conductive layer 82 which do not overlap with each other. The positive electrode 80 can be made of Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy, Ni/Co alloy, Pd/Au alloy, Pt/Au alloy, Ti/Au alloy, Cr/Au alloy, Sn/Au alloy alloy, Ta/Au alloy, TiN, TiWN _x (x≥0), WSi _y (y≥0), etc., or other similar metal materials. The transparent conductive layer 82 can be a metal conductive layer or a transparent oxide layer. The metal conductive layer is made of Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy, Pd/Au alloy, Pt/Au alloy, Cr/Au alloy, Ni/Au/Be alloy, Ni/Cr/Au alloy, One of Ni/Pt/Au alloy, Ni/Pd/Au alloy and other similar materials. The transparent oxide layer is made of ITO, CTO, ZnO:Al, ZnGa ₂ O ₄ , SnO ₂ :Sb, Ga ₂ O ₃ :Sn, AgInO ₂ :Sn, In ₂ O ₃ :Zn, CuAlO ₂ , LaCuOS, NiO, Composed of one of CuGaO ₂ and SrCu ₂ O ₂ .

Example 2

～20

之间、成长温度亦均介于600℃～1100℃之间。不同的氮化铟镓薄层722的氮化铟镓组成(即前述分子式的参数h)不一定相同。FIG. 3 is a schematic diagram of Embodiment 2 of the GaN-based light-emitting diode of the present invention. As shown in FIG. 3 , the embodiment 2 and the embodiment 1 have the same structure and growth method. The only difference is the material and structure used in the micro-roughening thin layer. In the second embodiment, the micro-roughened thin layer 72 is a short-period superlattice structure formed by alternately stacking the silicon nitride thin layer 721 and the indium gallium nitride thin layer 722 alternately. Each silicon nitride thin layer 721 is made of silicon nitride ( _Sif N _g N, 0<f, g<1) with its specific composition, and its thickness is between 2 ~20 The growth temperature is also between 600°C and 1100°C. The silicon nitride composition of different silicon nitride thin layers 721 (ie, the parameters f and g of the aforementioned molecular formula) are not necessarily the same. Each indium gallium nitride thin layer 722 is made of undoped indium gallium nitride (In _h Ga _1-h N, 0<h≤1) with its specific composition, and its thickness is between 2

~20

The growth temperature is also between 600°C and 1100°C. The InGaN composition (ie, the parameter h of the aforementioned molecular formula) of different InGaN thin layers 722 is not necessarily the same.

In the micro-roughened thin layer 72, the bottom layer (that is, directly on the p-type contact layer) can be a thin silicon nitride layer 721, on which a thin layer of indium gallium nitride 722 and a thin layer of silicon nitride 721 are sequentially stacked. ,So on and so forth. Alternatively, the bottom layer may also be a thin layer of InGaN 722 , on which a thin layer of Silicon Nitride 721 and a thin layer of InGaN 722 are sequentially stacked, and so on. The silicon nitride thin layer 721 and the indium gallium nitride thin layer 722 are stacked alternately and repeatedly in this way, and the number of repetitions is greater than or equal to two (that is, the number of layers of the silicon nitride thin layer 721 and the number of layers of the indium gallium nitride thin layer 722 are greater than or equal to two). The total thickness of the micro-roughened thin layer 72 is not more than 200

Example 3

～20

之间、成长温度亦均介于600℃～1100℃之间。不同的氮化硅薄层741的氮化硅组成(即前述分子式的参数i，j)不一定相同。每一个氮化铝铟镓薄层742，均是由未掺杂、具有其特定组成的氮化铝铟镓(Al_mIn_nGa_1-m-nN，0＜m，n＜1，m+n＜1)所构成，其厚度均介于2

～20

之间、成长温度亦均介于600℃～1100℃之间。不同的氮化铝铟镓薄层742的氮化铝铟镓组成(即前述分子式的参数m，n)不一定相同。FIG. 4 is a schematic view of Embodiment 3 of the gallium nitride-based light-emitting diode of the present invention. As shown in FIG. 4 , this embodiment 3 has the same structure and growth method as the above-mentioned embodiments 1 and 2. The only difference is the material and structure used in the micro-roughening thin layer. In the third embodiment, the micro-roughened thin layer 74 is a short-period superlattice structure formed by alternately stacking thin silicon nitride layers 741 and AlInGaN thin layers 742 . Each silicon nitride thin layer 741 is made of silicon nitride (Si _i N _j N, 0<i, j<1) with its specific composition, and its thickness is between 2

~20

The growth temperature is also between 600°C and 1100°C. The silicon nitride compositions of different silicon nitride thin layers 741 (ie, the parameters i, j of the aforementioned molecular formula) are not necessarily the same. Each AlInGaN thin layer 742 is made of undoped AlInGaN (Al _m In _n Ga _1-mn N, 0<m, n<1, m+n <1) constituted, its thickness is between 2

~20

The growth temperature is also between 600°C and 1100°C. The AlInGaN composition of different AlInGaN thin layers 742 (ie, the parameters m and n of the aforementioned molecular formula) are not necessarily the same.

In the micro-roughened thin layer 74, the bottom layer (that is, directly on the p-type contact layer) can be a thin silicon nitride layer 741, on which a thin layer of aluminum indium gallium nitride 742, a thin layer of silicon nitride 741, and so on. Alternatively, the bottom layer may also be a thin AlInGaN layer 742 , on which a thin SiN layer 741 , a thin AlInGaN layer 742 are stacked in sequence, and so on. The silicon nitride thin layer 741 and the aluminum indium gallium nitride thin layer 742 are stacked alternately and repeatedly in this manner, and the number of repetitions is greater than or equal to two (that is, the number of layers of the silicon nitride thin layer 741 and the number of layers of the aluminum indium gallium nitride thin layer 742 layers are greater than or equal to two). The total thickness of the micro-roughened thin layer 74 is not more than 200

In the foregoing three embodiments, the surface of the gallium nitride-based light-emitting diode is micro-roughened due to the growth of the silicon nitride material in the micro-roughened thin layer. In this way, the internal total reflection caused by the higher refractive index of the GaN-based light-emitting diodes than air can be avoided, thereby improving the external quantum efficiency and luminous efficiency of the GaN-based light-emitting diodes.

The above descriptions are only preferred embodiments for explaining the present invention, and are not intended to limit the present invention in any way. Therefore, any modification or change related to the present invention made under the same spirit of the invention should still include Within the scope of protection of the present invention.

Claims (3)

1. A gallium nitride-based light-emitting diode, characterized in that it comprises: The substrate is made of alumina single crystal, 6H-SiC, 4H-SiC, Si, ZnO, GaAs, spinel MgAl ₂ O ₄ and single crystal oxide whose lattice constant is close to that of nitride semiconductor; The buffer layer, which is located on one side of the substrate, is composed of aluminum gallium indium nitride Al _a Ga _b In _1-ab N with a specific composition, where 0≤a, b<1, a+b≤1; an n-type contact layer, located on the buffer layer, is made of gallium nitride-based materials; an active layer, which is located on the n-type contact layer and covers part of the upper surface of the n-type contact layer, and is made of indium gallium nitride; a negative electrode on the upper surface of the n-type contact layer not covered by the active layer; a p-type cladding layer, located on the active layer, made of p-type GaN-based material; a p-type contact layer, located on the p-type cladding layer, made of p-type gallium nitride; a thin micro-roughened layer on the p-type contact layer, Composed of silicon nitride Si _d Ne _e with a specific composition, the thickness is between

Between, where 0<d, e<1, Or it is composed of a short-period superlattice structure formed by stacking silicon nitride Si _f N _g N with a specific composition and undoped indium gallium nitride In _h Ga _1-h N with a specific composition, where 0< f, g<1, 0<h≤1, Or it is composed of a short-period superlattice structure formed by stacking silicon nitride Si _i N _j N with a specific composition and undoped aluminum indium gallium nitride Al _m In _n Ga _1-mn N with a specific composition, wherein 0<i, j<1, 0<m, n<1, m+n<1, And, the total thickness of the micro-roughened thin layer is not more than

The transparent conductive layer is a metal conductive layer or a transparent oxide layer that is located on the micro-roughened thin layer and covers part of the surface of the micro-roughened thin layer. The metal conductive layer is made of Ni/Au alloy, Ni/Pt alloy , Ni/Pd alloy, Pd/Au alloy, Pt/Au alloy, Cr/Au alloy, Ni/Au/Be alloy, Ni/Cr/Au alloy, Ni/Pt/Au alloy, Ni/Pd/Au alloy One is composed of ITO, CTO, ZnO:Al, ZnGa ₂ O ₄ , SnO ₂ :Sb, Ga ₂ O ₃ :Sn, AgInO ₂ :Sn, In ₂ O ₃ :Zn, CuAlO ₂ , LaCuOS, NiO, CuGaO ₂ , SrCu ₂ O ₂ constituted by one; and The positive electrode, which is located on the surface of the micro-roughened thin layer not covered by the transparent conductive layer, is made of Ni/Au alloy, Ni/Pt alloy, Ni/Pd alloy, Ni/Co alloy, Pd/Au alloy, Composed of one of Pt/Au alloy, Ti/Au alloy, Cr/Au alloy, Sn/Au alloy, Ta/Au alloy, TiN, TiWN _x , WSi _y , where x≥0, y≥0. 2. The gallium nitride-based light-emitting diode according to claim 1, wherein the micro-roughened thin layer is composed of a silicon nitride Si _f N _g N thin layer with a specific composition and an indium gallium nitride Indium with a specific composition. A short-period superlattice structure formed by alternating and repeated lamination of _h Ga _1-h N thin layers, the number of repetitions is at least twice, and the total thickness does not exceed

The thickness of each silicon nitride Si _f N _g N thin layer is between

Between, the thickness of each indium gallium nitride In _h Ga _1-h N thin layer is between Between, where 0<f, g<1, 0<h≤1. 3. The gallium nitride-based light-emitting diode according to claim 1, wherein the micro-roughened thin layer is composed of a silicon nitride Si _i N _j N thin layer with a specific composition and an aluminum indium gallium nitride with a specific composition A short-period superlattice structure formed by alternately stacking Al _m In _n Ga _1-mn N thin layers, the number of repetitions is at least twice, and the total thickness does not exceed

The thickness of each silicon nitride Si _i N _j N thin layer is between

Between, the thickness of each aluminum indium gallium nitride Al _m In _n Ga _1-mn N thin layer is between

Between, where 0<i, j<1, 0<m, n<1, m+n<1.

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