JP2004356442A - Group iii nitride system compound semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the electrostatic withstanding voltage of a group III nitride system compound semiconductor light emitting element without deteriorating its light emitting characteristic. <P>SOLUTION: A multiple layer (electrostatic withstanding voltage enhancing layer) 105 comprising five stacked pairs of 3-nm thick non-doped In<SB>0.03</SB>Ga<SB>0.97</SB>N layers 1051 and 20 nm thick non-doped GaN layers 1052 is formed to a negative electrode side of a light emitting layer 106 of a multiquantum well structure comprising three stacked pairs of 3 nm thick non-doped In<SB>0.2</SB>Ga<SB>0.8</SB>N well layers 1061 and 20 nm thick non-doped barrier layers 1062. The multiple layer (electrostatic withstanding voltage enhancing layer) 105 plays a role of extending an applied voltage over a wide range of an n electrode side of the light emitting layer without concentrating the applied voltage onto part of the n electrode side of the light emitting layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a group III nitride compound semiconductor light emitting device. The present invention provides a group III nitride compound semiconductor light emitting device having a high electrostatic withstand voltage.
[0002]
[Prior art]
Group III nitride-based compound semiconductor light-emitting devices have been widely used as light-emitting devices in the green, blue, or ultraviolet region, but there is still room for improvement in various characteristics of the group III nitride-based compound semiconductor light-emitting devices other than the emission intensity. In particular, the electrostatic withstand voltage is much lower than that of a gallium / arsenic-based light-emitting element or an indium / phosphorus-based light-emitting element, and a significant improvement in electrostatic withstand voltage is expected. Here, the following proposals have been made to improve the electrostatic withstand voltage of a group III nitride compound semiconductor light emitting device.
[0003]
[Patent Document 1] JP-A-11-191639 [Patent Document 2] JP-A-2000-68594 [Patent Document 3] JP-A-2000-244072 [Patent Document 4] JP-A-2001-203385 [0004] ]
[Problems to be solved by the invention]
Even with these techniques, the electrostatic breakdown voltage of the group III nitride compound semiconductor light emitting device is not sufficient, and the electrostatic breakdown voltage has a trade-off relationship with the light emission intensity and the driving voltage.
[0005]
Accordingly, an object of the present invention is to improve the electrostatic withstand voltage without deteriorating the light emission intensity and the driving voltage with respect to the above prior art.
[0006]
[Means for Solving the Problems]
In order to solve the above problem, according to the means of claim 1, in a group III nitride compound semiconductor light emitting device having a light emitting layer of a multiple quantum well structure, non-doped In is provided on the n electrode side of the light emitting layer. _It has a multi-layer of a layer made of xGa _1-xN (0 <x <1) and a layer made of non-doped GaN, and the well layer of the light emitting layer having the multiple quantum well structure contains at least indium (In). group III nitride compound semiconductor _{Al y Ga 1-y-z} In z N (0 ≦ y <1, 0 <z ≦ 1) _{consists, In x Ga 1-x N} (0 forming the multi-layer < The composition x of indium (In) in the layer composed of x <1) is smaller than the composition z of indium (In) in the well layer of the light emitting layer having the multiple quantum well structure.
[0007]
Further, according to the means described in claim 2, the composition x of indium (In) layer of the non-doped _{In x Ga 1-x N (} 0 <x <1) is 0.02 or more 0.07 It is characterized by the following. Further, according to the means described in claim 3, wherein the thickness of the layer made of the non-doped _{In x Ga 1-x N (} 0 <x <1) is 0.5nm or more 6nm or less . According to a fourth aspect of the present invention, the ratio of the thickness of the non-doped In _x Ga _1-x N (0 <x <1) to the thickness of the well layer of the light emitting layer is as follows: It is 0.1 or more and 2 or less. According to a fifth aspect of the present invention, a ratio of the thickness of the non-doped GaN layer to the thickness of the barrier layer of the light emitting layer is 0.5 or more and 4 or less. . Moreover, said the According to the measures of claim 6, the number of layers consisting of the said non-doped multiple layer _{In x Ga 1-x N (} 0 <x <1) is 1 to 7 I do.
[0008]
[Action and effect of the invention]
As shown in the examples below, III nitride compound containing indium (In) to form a light emitting layer of the present invention a semiconductor _{Al y Ga 1-y-z} In z N (0 ≦ y <1, 0 <z ≦ 1) a layer comprising a well layer of low doped compositions of indium (in) than _{in x Ga 1-x N (} 0 <x <1) made of light-emitting multiple layers of a layer consisting of undoped GaN By providing the layer on the n-electrode side, it was possible to obtain a group III nitride-based compound semiconductor light-emitting device in which the electrostatic breakdown voltage was improved and the emission intensity and the driving voltage were not deteriorated. Regarding the effect of producing such an effect, the multi-layer of the present invention exerts an effect that the applied voltage spreads over a wide range on the n-electrode side of the light-emitting layer without being concentrated on a part of the light-emitting layer on the n-electrode side. Conceivable.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
A preferred embodiment of the present invention will be described. First, the term "non-doped" used in the present application merely means that dopant impurities are not intentionally introduced when the layer is intentionally formed, and does not exclude those in which "dopant" is mixed for some technical reason. . The technical reasons include migration from an adjacent layer, contamination due to incomplete switching of introduced materials at the boundary between different layers, or contamination that is always generated in a very small amount due to poor cleaning of manufacturing equipment. Nations are given. These layers into which “dopants” are unintentionally mixed are substantially included in the “non-doped layer” referred to in the present application.
[0010]
A multiple quantum well structure forming the light emitting layer is at least indium III nitride compound containing (In) semiconductor _{Al y Ga 1-y-z} In z N (0 ≦ y <1, 0 <z ≦ 1) Including a well layer. Structure of the light-emitting layer, for example doped, or a well layer made of _{Ga 1-z In z N (} 0 <z ≦ 1) undoped, III group nitride of any composition larger band gap than the well layer Barrier layer made of a compound-based compound semiconductor AlGaInN. Preferred examples are the barrier layer comprising a well layer and an undoped GaN undoped _{Ga 1-z In z N (} 0 <z ≦ 1).
[0011]
Multiple layer provided on the n-electrode side of the light-emitting layer which is a main feature of the present invention, at least indium (an In) III nitride compound including semiconductor _Al to form a light emitting layer _{y Ga 1-y-z In} z N Non-doped In _x Ga _1-x N (0 <x <) with a composition x of indium (In) smaller than the composition z of indium (In) in the well layer composed of (0 ≦ y <1, 0 <z ≦ 1) 1) and a layer made of non-doped GaN. In this case, the composition x of indium layers of undoped _{In x Ga 1-x N (} 0 <x <1) to form the multi-layer (In) are 0.02 to 0.07, more preferably It is preferably from 0.03 to 0.05.
[0012]
The film thickness of the non-doped a _In x _Ga 1-x N of the multi-layer provided on the n-electrode side of the light-emitting layer (0 <x <1) layer is preferably at 0.5nm or more 6nm or less, 0. More preferably, it is 5 nm or more and 4 nm or less. Although referred emission characteristics below, undoped _{In x Ga 1-x N (} 0 <x <1) film thickness of a layer consisting of more than 6nm and the driving voltage Vf is found to significantly increase. If the thickness is less than 0.5 nm, it is difficult to adjust the thickness of the film. On the other hand, it has been found that the multi-layered layer made of non-doped GaN does not cause a significant change in device characteristics at least in the range of 10 to 40 nm. Ratio undoped _In x _Ga 1-x N thickness of the thickness of the light-emitting layer of the well layer of the layer made of (0 <x <1) the multiple layer is preferably 0.1 to 2. More desirably adjusting the thickness of the layer made of undoped In x _Ga 1-x _N of the multi-layer below the thickness of the well layer of the light-emitting layer _{(0 <x} <1). On the other hand, it is desirable that the ratio of the thickness of the multilayer non-doped GaN layer to the thickness of the light-emitting layer of the barrier layer is 0.5 or more and 4 or less. More preferably, it is desirable to adjust the thickness of the multilayer non-doped GaN layer to be equal to or greater than the thickness of the barrier layer of the light emitting layer.
[0013]
The number of non-doped In _x Ga _1-x N (0 <x <1) layers of the multi-layer provided on the n-electrode side of the light emitting layer is desirably 1 or more, and more preferably 1 or more. It is better to do the following.
[0014]
The group III nitride-based compound semiconductor light-emitting device according to the present invention can have any configuration other than the above-described limitation of the main configuration of the invention. The light emitting element may be a light emitting diode (LED), a laser diode (LD), a photocoupler, or any other light emitting element. In particular, any manufacturing method can be used as a method for manufacturing the group III nitride compound semiconductor light emitting device according to the present invention.
[0015]
Specifically, sapphire, spinel, Si, SiC, ZnO, MgO, a group III nitride-based compound single crystal, or the like can be used as a substrate for crystal growth. As a method for growing a group III nitride-based compound semiconductor layer, a molecular beam vapor deposition (MBE), a metalorganic vapor phase epitaxy (MOCVD), a halide vapor phase epitaxy (HDVPE), a liquid phase epitaxy, or the like can be used. Is valid.
[0016]
Group III nitride semiconductor layer of the electrode forming layer and the like is expressed by at least _{Al x Ga y In 1-x} -y N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) 2 It can be formed of a group III nitride compound semiconductor composed of a ternary, ternary, or quaternary semiconductor. Some of these group III elements may be replaced with boron (B) or thallium (Tl), and some of nitrogen (N) may be replaced with phosphorus (P), arsenic (As), antimony (Sb). ) And bismuth (Bi).
[0017]
Further, when an n-type group III nitride compound semiconductor layer is formed using these semiconductors, Si, Ge, Se, Te, C, etc. are added as n-type impurities, and p-type impurities are added. , Zn, Mg, Be, Ca, Sr, Ba and the like can be added.
[0018]
By the means of the present invention described above, the above problems can be effectively or rationally solved.
[0019]
〔Example〕
FIG. 1 is a schematic sectional view of a semiconductor light emitting device 100 according to an embodiment of the present invention. In the semiconductor light emitting device 100, as shown in FIG. 1, a buffer layer 102 having a thickness of about 15 nm made of aluminum nitride (AlN) is formed on a sapphire substrate 101 having a thickness of about 300 μm. A layer 103 made of GaN having a thickness of about 500 nm is formed, and an n-type contact layer 104 made of GaN doped with silicon (Si) at 1 × 10 ¹⁸ / cm ³ and having a thickness of about 5 μm (high carrier concentration n ⁺ Layer) is formed.
[0020]
Further, on the n-type contact layer 104, a multilayer structure in which five pairs of a layer 1051 made of non-doped In _0.03 Ga _0.97 N and a layer 1052 made of non-doped GaN having a thickness of 20 nm are stacked. (Electrostatic breakdown voltage improving layer) 105 is formed. Further thereon, three pairs of a well layer 1061 made of non-doped In _0.2 Ga _0.8 N having a thickness of 3 nm and a barrier layer 1062 made of non-doped GaN having a thickness of 20 nm are laminated to emit light having a multiple quantum well structure. A layer 106 is formed.
[0021]
Further, a p-type layer 107 made of p-type Al _0.15 Ga _0.85 N doped with Mg at 2 × 10 ¹⁹ / cm ³ and having a thickness of 25 nm is formed on the light-emitting layer 106. On the p-type layer 107, a p-type contact layer 108 of 100 nm-thick p-type GaN doped with 8 × 10 ¹⁹ Mg was formed.
[0022]
A translucent thin-film p-electrode 110 is formed on the p-type contact layer 108 by metal deposition, and an n-electrode 140 is formed on the n-type contact layer 104. The translucent thin-film p-electrode 110 has a first layer 111 made of cobalt (Co) having a thickness of about 1.5 nm directly bonded to the p-type contact layer 108 and a gold ( Au) and the second layer 112 made of Au).
[0023]
The thick p-electrode 120 includes a first layer 121 of vanadium (V) having a thickness of about 18 nm, a second layer 122 of gold (Au) having a thickness of about 15 μm, and aluminum (Al) having a thickness of about 10 nm. And a third layer 123 made of light-transmitting thin-film p-electrode 110.
[0024]
The n-electrode 140 having a multilayer structure is composed of a first layer 141 of vanadium (V) having a thickness of about 18 nm and aluminum (Al) having a thickness of about 100 nm from a part of the n-type contact layer 104 which is partially exposed. And a second layer 142 made of these layers.
[0025]
Further, a protective film 130 made of a SiO ₂ film is formed on the uppermost portion.
A reflection metal layer 150 made of aluminum (Al) having a thickness of about 500 nm is formed by metal evaporation at the lowermost portion on the outside corresponding to the bottom surface of the sapphire substrate 101. The reflective metal layer 150 may be made of a metal such as Rh, Ti, and W, or a nitride such as TiN and HfN.
[0026]
[Comparison with Other Multi-Layer Configurations for Example]
The electrostatic withstand voltage, drive voltage Vf, and total radiant flux (emission intensity) of the above embodiment will be described below with reference to the drawings in comparison with the case where the multilayer structure is partially changed. The electrostatic withstand voltage was measured using a machine model equation with a pulse voltage of 0Ω, 200 F, and 30 ns.
[0027]
FIGS. 2A, 2B, and 2C respectively show the electrostatic breakdown voltage, drive voltage Vf, and total radiant flux of the device of the above-described embodiment by using a non-doped In _0.03 Ga _0.97 N film having a thickness of 3 nm. Is a diagram showing a case where the film thickness of a layer 1051 made of 1.5 nm to 10 nm. The layer 1051 made of non-doped In _0.03 Ga _0.97 N can have a high electrostatic withstand voltage and a low driving voltage Vf in the case of an element having a thickness of 1.5 nm to 3 nm, but has a thickness of 10 nm. In the case of the element, a result was obtained in which the electrostatic withstand voltage was slightly lower and the drive voltage Vf was higher. On the other hand, the total radiant flux (emission intensity) was not significantly affected by the film thickness.
[0028]
3 (a), (b) and (c) show the electrostatic breakdown voltage, drive voltage Vf and total radiant flux of the device of the above embodiment, respectively, using a non-doped In _0.03 Ga _0.97 N film having a thickness of 3 nm. FIG. 10 is a diagram showing a case where the In composition of a layer 1051 made of (3% In composition) is 0.01 (1%) to 0.08 (8%). The layer 1051 made of non-doped InGaN can lower the driving voltage Vf in the case of an element having an In composition of 0.03 (3%) to 0.05 (5%), but has an In composition of 0.01 (1%). Alternatively, in the case of the element set to 0.08 (8%), the result that the drive voltage Vf becomes high was obtained. On the other hand, the total radiant flux (emission intensity) was not significantly affected by the film thickness. The electrostatic withstand voltage was slightly improved in a preferable range of the drive voltage Vf.
[0029]
4 (a), (b) and (c) show the electrostatic breakdown voltage, drive voltage Vf and total radiant flux of the device of the above embodiment, respectively. FIG. 2 is a diagram showing the case of a device doped with 1 × 10 ¹⁸ / cm ³ . The driving voltage of the layer 1052 made of GaN can be lowered in the case of a non-doped element, but the driving voltage Vf is increased in the case of an element doped with silicon (Si) at 1 × 10 ¹⁸ / cm ^3. Was done. On the other hand, the electrostatic withstand voltage and the total radiant flux (emission intensity) were not significantly affected by the difference between doping / non-doping.
[0030]
FIGS. 5A, 5B, and 5C respectively show the electrostatic breakdown voltage, drive voltage Vf, and total radiant flux of the device of the above-described embodiment by using a non-doped In _0.03 Ga _0.97 N film having a thickness of 3 nm. FIG. 6 is a diagram showing a case where a layer 1051 made of silicon is doped with silicon (Si) at 1 × 10 ¹⁸ / cm ³ . The layer 1051 made of In _0.03 Ga _0.97 N can have a high electrostatic withstand voltage and a low driving voltage when it is non-doped. However, in the case of a device doped with silicon (Si) at 1 × 10 ¹⁸ / cm ^3, The result that the electrostatic withstand voltage was low and the drive voltage Vf was high was obtained. On the other hand, the total radiant flux (emission intensity) was not significantly affected by the difference between doped and non-doped.
[0031]
FIGS. 6A, 6B, and 6C respectively show the electrostatic breakdown voltage, drive voltage Vf, and total radiant flux of the device of the above-described embodiment by using a non-doped In _0.03 Ga _0.97 N film having a thickness of 3 nm. FIG. 10 is a diagram showing a case where the number of pairs of a layer 1051 made of GaN and a layer 1052 made of non-doped GaN having a thickness of 20 nm is 3 to 10 pairs. The multi-layer 105 has a high electrostatic withstand voltage and a low driving voltage Vf when the configuration is composed of three pairs or five pairs. Was obtained. On the other hand, the total radiant flux (emission intensity) was not largely affected by the difference in the number of pairs.
[0032]
FIGS. 7A, 7B, and 7C respectively show the electrostatic breakdown voltage, the driving voltage Vf, and the total radiant flux of the device of the above-described embodiment by using a non-doped In _0.03 Ga _0.97 N film having a thickness of 3 nm. The structure of the layer 1051 made of non-doped GaN and the layer 1052 made of non-doped GaN having a thickness of 20 nm is changed to the layer made of non-doped In _0.03 Ga _0.97 N having a thickness of 3 nm and the non-doped Al _0.2 Ga _0.8 N having a thickness of 20 nm. FIG. 7 is a diagram showing the case of a device having a layer made of non-doped GaN and a device having a layer of non-doped GaN having a thickness of 3 nm and non-doped Al _0.2 Ga _0.8 N having a thickness of 20 nm. The multi-layer 105 has a high electrostatic withstand voltage and a high driving voltage when its configuration is composed of a layer 1051 made of non-doped In _0.03 Ga _0.97 N having a thickness of 3 nm and a layer 1052 made of non-doped GaN having a thickness of 20 nm. However, in the case of an element having the other two configurations, a result was obtained in which the electrostatic withstand voltage was low and the drive voltage Vf was high. On the other hand, the total radiant flux (emission intensity) was not significantly affected by the difference in the composition of the two layers constituting the multilayer 105.
[0033]
The present invention is not limited to the above embodiment, and various other modifications are possible. For example, each group III nitride-based compound semiconductor layer may be a binary to quaternary AlGaInN having an arbitrary mixed crystal ratio. More specifically, _{"Al x Ga y In 1-x} -y N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ x + y ≦ 1) " made general formula binary represented, 3-way (GaInN, AlInN, AlGaN) or a quaternary (AlGaInN) group III nitride compound semiconductor can also be used. Further, a part of N of the compound may be replaced with a group V element such as P or As. In the above embodiment, the protective film 130 is formed, but the protective film 130 may be omitted. In this example, a reflective metal layer is formed on the back surface of the sapphire substrate, and a light-transmitting thin film p-electrode is provided on the p-electrode side. For this purpose, an electrode layer serving also as a light reflecting layer may be provided on the p-electrode side without forming the reflective metal layer on the back surface of the sapphire substrate.
[Brief description of the drawings]
FIG. 1 is a sectional view of a semiconductor light emitting device 100 according to an embodiment of the present invention.
FIGS. 2A, 2B, and 2C respectively show the relationship between the thickness of a layer 1051 made of non-doped In _0.03 Ga _0.97 N, electrostatic withstand voltage, drive voltage Vf, and total radiant flux. FIG.
FIGS. 3A, 3B, and 3C are characteristic diagrams showing the relationship between the In composition of a layer 1051 made of non-doped InGaN, electrostatic withstand voltage, drive voltage Vf, and total radiant flux, respectively.
4 (a), (b), and (c) show the relationship between the electrostatic withstand voltage, the driving voltage Vf, and the total radiant flux when the layer 1052 made of GaN is and is not doped with silicon, respectively. Characteristic diagram.
FIGS. 5A, 5B, and 5C respectively show an electrostatic withstand voltage, a driving voltage Vf, and a driving voltage when a layer 1051 made of In _0.03 Ga _0.97 N is doped with silicon; FIG. 4 is a characteristic diagram showing a relationship between total radiant fluxes.
FIGS. 6A, 6B, and 6C are characteristic diagrams showing the relationship among the number of pairs of the multilayer 105, electrostatic withstand voltage, drive voltage Vf, and total radiant flux, respectively.
FIGS. 7A, 7B, and 7C are characteristic diagrams showing the relationship between the composition of the two layers constituting the multilayer 105, the electrostatic withstand voltage, the driving voltage Vf, and the total radiant flux, respectively.
[Explanation of symbols]
Reference Signs List 100 semiconductor light emitting element 101 sapphire substrate 102 buffer layer 103 non-doped GaN layer 104 high carrier concentration n ⁺ layer 105 multilayer (electrostatic breakdown voltage improving layer)
106 light-emitting layer 107 p-type semiconductor layer 108 p-type contact layer 110 translucent thin-film p-electrode 120 p-electrode 130 protective film 140 n-electrode 150 reflective metal layer

Claims (6)

In a group III nitride compound semiconductor light emitting device having a light emitting layer of a multiple quantum well structure,
On the n-electrode side of the light emitting layer, there is provided a multi-layer of a layer made of non _- doped In _x Ga _1-x N (0 <x <1) and a layer made of non-doped GaN,
The group III nitride compound well layer of the light emitting layer contains at least indium (In) of the multi-quantum well structure semiconductor _{Al y Ga 1-y-z} In z N (0 ≦ y <1, 0 <z ≦ 1) Consisting of
The composition x of indium (In) in the layer composed of In _x Ga _1-x N (0 <x <1) forming the multiple layer is the same as that of indium (In) in the well layer of the light emitting layer having the multiple quantum well structure. A group III nitride-based compound semiconductor light-emitting device characterized by having a composition smaller than z. The composition x of indium (In) layer of the non-doped _{In x Ga 1-x N (} 0 <x <1) is claimed in claim 1, characterized in that 0.02 to 0.07 III-nitride-based compound semiconductor light-emitting device. 3. The group III nitride according to claim 1, wherein a thickness of the non-doped layer of In _x Ga _1-x N (0 <x <1) is 0.5 nm or more and 6 nm or less. 4. Compound semiconductor light emitting device. The ratio of the thickness of said non-doped _{In x Ga 1-x N (} 0 <x <1) layer of thickness the light emitting layer of the well layer is characterized in that 0.1 to 2 The group III nitride compound semiconductor light emitting device according to claim 1. 4. The light emitting device according to claim 1, wherein a ratio of a thickness of the non-doped GaN layer to a thickness of the barrier layer of the light emitting layer is 0.5 or more and 4 or less. 13. The group III nitride compound semiconductor light emitting device according to claim 1. Any one of claims 1 to 5, wherein the number of layers consisting of the said non-doped multiple layer _{In x Ga 1-x N (} 0 <x <1) is 1 to 7 A group III nitride compound semiconductor light emitting device according to item 1.

Images