JP2005183780A - Manufacturing method of nitride-based iii group compound semiconductor light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve light emission output of a nitride-based III group compound semiconductor light emitting element by improving crystallinity of a p-layer formed in contact with a light emitting layer. <P>SOLUTION: The semiconductor light emitting element 1000 is formed of a GaN buffer layer 101, an n-type contact layer 102 formed of GaN, an n-layer 103 formed of Al<SB>0.12</SB>Ga<SB>0.88</SB>N, a light emission layer 104 of a single quantum well structure (SQW) holding a 2 nm-thick nondoped well layer consisting of Al<SB>0.005</SB>In<SB>0.045</SB>Ga<SB>0.95</SB>N between barrier layers, a block layer 105 consisting of Al<SB>0.16</SB>Ga<SB>0.84</SB>N, a p-type contact layer 106 consisting of Al<SB>0.02</SB>Ga<SB>0.98</SB>N, electrodes 110, 120, 140, a protecting film 130, and a reflection film 150 on a sapphire substrate 100. The relation of the epitaxial growth temperature T<SB>p</SB>of a p-side layer (105) in contact with the light emission layer, the epitaxial growth temperature T<SB>n</SB>of an n-side layer (103) in contact with the light emission layer and the epitaxial growth temperature T<SB>L</SB>(800°C or higher) of the light emission layer 106 is made 0<T<SB>n</SB>-T<SB>p</SB>≤(T<SB>n</SB>-T<SB>L</SB>)/5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a group III nitride compound semiconductor light emitting device. The present invention is particularly effective for a group III nitride compound semiconductor light emitting device emitting in the ultraviolet region.

Development of a light emitting element having a short wavelength in which an emission wavelength exists mainly in the ultraviolet region has been advanced, and the following applications have been filed.
JP-A-6-268259 JP 2001-024223 A

  In a light emitting device having a single quantum well structure or a multiple quantum well structure, when the barrier layer is made of AlGaN containing aluminum in the composition and the well layer is made of AlInGaN containing aluminum and indium in the composition, it is formed in contact with the light emitting layer. It has been found that if the p layer has poor crystallinity, it is difficult to improve the light emission output.

  Accordingly, an object of the present invention is to improve the light emission output of the group III nitride compound semiconductor light emitting device by improving the crystallinity of the p layer formed in contact with the light emitting layer.

In order to solve the above-described problems, the present invention is characterized in that, in a method for manufacturing a light-emitting element formed by stacking group III nitride compound semiconductors by epitaxial growth, it substantially contributes to light emission, and the composition has at least indium. The growth temperature T _{L of the} light emitting layer containing (In) (800 ° C. or higher), the growth temperature T _n of the n-type semiconductor layer in contact with the light emitting layer, and the growth temperature T _p of the p-type semiconductor layer in contact with the light emitting layer ,
T _n −T _p is positive and T _n −T _L is 1/3 or less, or 1/4 or less, or 1/5 or less (Claims 1 to 3). Here, the growth temperature refers to the temperature of the substrate in the epitaxial growth.

Another feature is that at least the light emitting layer, the n-type semiconductor layer, and the p-type semiconductor layer are formed by metal organic vapor phase epitaxy. Alternatively, the temperature T _p is 1000 ° C. or higher.

  Another feature is that the emission wavelength peak of the light emitting layer is 380 nm or less. Furthermore, the light emitting layer is a single quantum well or a multiple quantum well.

  Usually, the n-type layer is formed by epitaxial growth at about 1000 to 1150 ° C. in order to improve the crystallinity of each layer immediately below the light emitting layer. On the other hand, when the light emitting layer contains indium, the epitaxial growth of the p-type layer was not performed at a very high temperature. That is, if epitaxial growth of the p-type layer is performed at an excessively high temperature, the crystallinity of the light-emitting layer containing indium is deteriorated, and a dopant such as magnesium for forming the p-type layer is diffused into the light-emitting layer. It was because it was thought that it deteriorated remarkably. Except for the influence on the light emitting layer, the p-type layer containing aluminum in its composition can have its growth temperature as high as possible, that is, as high as the n-side layer.

  In contrast, the inventor of the present invention makes the temperature difference lower than the epitaxial growth temperature of the n-type layer while making the epitaxial growth temperature of the p-type layer lower than the epitaxial growth temperature of the n-type layer and the epitaxial growth temperature of the light emitting layer. It has been found that the light emission output can be improved by setting it to 3 or less, 1/4 or less, or 1/5 or less. This is presumably because hole injection from the p layer into the light emitting layer becomes ideal as the crystallinity of the p layer improves. On the other hand, the influence on the light emitting layer, that is, the deterioration of the crystallinity of the light emitting layer and the diffusion of the dopant are more significant than the improvement of the crystallinity of the p layer by shortening the growth time (thinning of the p layer) There was no.

Since the p-type layer generally contains aluminum in its composition, the growth temperature T _p may be close to the growth temperature T _n of the n-type layer, for example, if the influence on the light emitting layer is excluded. On the other hand, as indicating the lower limit of the growth temperature T _p, the growth temperature of the light emitting layer as a T _L, if T _n -T _p exceeds 1/3 of T _n -T _L, p-type layer including aluminum on the composition Becomes poor in crystallinity and cannot be used as a method for manufacturing a light-emitting element.

  The group III nitride compound semiconductor light-emitting device according to the present invention can have any configuration other than the limitation related to the main configuration of the present 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 a group III nitride compound semiconductor light emitting device according to the present invention.

  Specifically, sapphire, spinel, Si, SiC, ZnO, MgO, a group III nitride compound single crystal, or the like can be used as a substrate for crystal growth. As a method for crystal growth of the group III nitride compound semiconductor layer, metal organic vapor phase epitaxy (MOVPE) is preferable, but molecular beam vapor phase epitaxy (MBE) and hydride vapor phase epitaxy (HVPE) are used. Also good.

Electrode forming layer other Group III nitride semiconductor layer is expressed by at least _{Al x Ga y In 1-xy} N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) 2 A group III nitride compound semiconductor made of a ternary, ternary, or quaternary semiconductor can be used. Some of these group III elements may be replaced by boron (B) and thallium (Tl), and part of nitrogen (N) may be phosphorus (P), arsenic (As), antimony (Sb ) Or bismuth (Bi).

  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 used as p-type impurities. Zn, Mg, Be, Ca, Sr, Ba and the like can be added.

  By the above means of the present invention, the above-mentioned problem can be effectively or rationally solved.

FIG. 1 is a cross-sectional view of a group III nitride compound semiconductor light emitting device 1000 according to a specific embodiment of the present invention. In the semiconductor light emitting device 1000, as shown in FIG. 1, a buffer layer 101 made of gallium nitride (GaN) and having a thickness of about 25 nm is formed on a sapphire substrate 100 having a thickness of about 100 μm, and silicon ( An n-type contact layer 102 (high carrier concentration n ⁺ layer) having a film thickness of about 4 μm made of GaN having an electron concentration of 5 × 10 ¹⁸ / cm ³ by doping Si) is formed.

On the n-type contact layer 102, an n-layer 103 having a thickness of about 200 nm made of Al _0.12 Ga _0.88 N doped with silicon (Si) to an electron concentration of 5 × 10 ¹⁸ / cm ³ is formed. ing.

A light emitting layer 104 having a single quantum well structure (SQW) is formed on the n layer 103. The light emitting layer 104 having a single quantum well structure (SQW) includes a barrier layer 1041 made of non-doped Al _0.13 Ga _0.87 N having a thickness of 12 nm and a well layer 1042 made of non-doped Al _0.005 In _0.045 Ga _0.95 N having a thickness of 2 nm. And a barrier layer 1043 made of non-doped Al _0.13 Ga _0.87 N having a thickness of 12 nm.

A 40 nm-thick p-type block made of Al _0.16 Ga _0.84 N doped with magnesium (Mg) to a hole concentration of 5 × 10 ¹⁷ / cm ³ on the light emitting layer 104 having a single quantum well structure (SQW) Layer 105 is formed. On the p-type block layer 105, a p-type contact layer 106 having a film thickness of about 60 nm made of Al _0.02 Ga _0.98 N doped with magnesium (Mg) to a hole concentration of 5 × 10 ¹⁷ / cm ³ was formed.

  Further, a translucent thin film p-electrode 110 formed by metal vapor deposition is formed on the p-type contact layer 106, and an n-electrode 140 is formed on the n-type contact layer 102. The translucent thin film p-electrode 110 includes a first layer 111 made of cobalt (Co) having a thickness of about 1.5 nm directly bonded to the p-type contact layer 106 and gold (Au) having a thickness of about 6 nm bonded to the cobalt film. ) And the second layer 112.

  The thick p-electrode 120 includes a first layer 121 made of vanadium (V) having a thickness of about 18 nm, a second layer 122 made of gold (Au) having a thickness of about 15 μm, and aluminum (Al) having a thickness of about 10 nm. The third layer 123 is formed by sequentially laminating the translucent thin film p-electrode 110 from above.

  The n-electrode 140 having a multilayer structure is formed of a first layer 141 made of vanadium (V) having a thickness of about 18 nm and an aluminum (Al) having a thickness of about 100 nm from above a part of the n-type contact layer 102 exposed. It is comprised by laminating | stacking the 2nd layer 142 which consists.

A protective film 130 made of a SiO ₂ film is formed on the top.
A reflective metal layer 150 made of aluminum (Al) with a film thickness of about 500 nm is formed on the lowermost part of the outer side corresponding to the bottom surface of the sapphire substrate 100 by metal deposition. The reflective metal layer 150 may be a metal such as Rh, Ti, or W, or a nitride such as TiN or HfN.

The light emitting device 1000 having the above-described configuration was manufactured as follows. The light-emitting element 1000 was manufactured by metal organic chemical vapor deposition (hereinafter abbreviated as “MOVPE”). The gases used were ammonia (NH ₃ ), carrier gas (H ₂ and N ₂ ), trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”), trimethylaluminum (Al (CH ₃ ) ₃ ) (Hereinafter referred to as “TMA”), trimethylindium (In (CH ₃ ) ₃ ) (hereinafter referred to as “TMI”), silane (SiH ₄ ) and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (Hereinafter referred to as “CP ₂ Mg”).

First, a single crystal substrate 100 having a C-plane main surface cleaned by organic cleaning and heat treatment is mounted on a susceptor mounted in a reaction chamber of a MOVPE apparatus. Next, the substrate 100 was baked at a temperature of 1100 ° C. while flowing H ₂ into the reaction chamber at normal pressure.
Next, the temperature of the substrate 100 was lowered to 500 ° C., and H ₂ , NH ₃ and TMG were supplied to form a GaN buffer layer 101 with a film thickness of about 25 nm.

Next, the temperature of the substrate 100 is kept at 1075 ° C., H ₂ , NH ₃ , TMG, and silane are supplied, and an n-type contact layer made of GaN having a film thickness of about 4 μm and a carrier concentration of 5 × 10 ¹⁸ / cm ³ 102 was formed. Thereafter, an n layer 103 having a film thickness of about 200 nm made of Al _0.12 Ga _0.88 N with an electron concentration of 5 × 10 ¹⁸ / cm ³ is formed while controlling the supply amount of H ₂ , NH ₃ , TMG, TMA, and silane. did.

Next, the temperature of the substrate 100 is lowered to 825 ° C., and the supply amount of N ₂ or H ₂ , NH ₃ , TMG, TMA, and TMI is controlled, and from 12 nm thick non-doped Al _0.13 Ga _0.87 N A barrier layer 1041 composed of non-doped Al _0.005 In _0.045 Ga _0.95 N with a thickness of 2 nm, and a barrier layer 1043 composed of non-doped Al _0.13 Ga _0.87 N with a thickness of 12 nm. A light emitting layer 104 having a quantum well structure was formed.

Next, the temperature of the substrate 100 is maintained at 1025 ° C., and N ₂ or H ₂ , NH ₃ , TMG, TMA, and CP ₂ Mg are supplied while being controlled, and Al _0.16 Ga _0.84 N doped with magnesium (Mg). A p-type block layer 105 having a thickness of 40 nm and a p-type contact layer 106 having a thickness of about 60 nm made of Al _0.02 Ga _0.98 N doped with magnesium (Mg) were sequentially formed.

Thereafter, the p-type block layer 105 and the p-type contact layer 106, which are p-side layers, are made p-type to form p-type layers having hole concentrations of 5 × 10 ¹⁷ / cm ³ and 5 × 10 ¹⁷ / cm ³ , respectively. After that, each electrode (110, 120, 140), protective film 130 and reflective metal layer 150 were formed.

In the above embodiment, the growth temperature in the epitaxial growth of the p-type block layer 105 and the p-type contact layer 106 which are p-side layers is changed to 975 ° C., 1000 ° C., 1025 ° C., and 1050 ° C. The electroluminescence intensity was measured. This is shown in FIG. As shown in FIG. 2, when the epitaxial growth temperature of the p-side layer is 975 ° C., the electroluminescence (EL) intensity varies and the EL intensity is small. As the epitaxial growth temperature of the p-side layer is increased to 1000 ° C., 1025 ° C., and 1050 ° C., the variation in electroluminescence (EL) intensity decreases and the EL intensity increases. At this time, the epitaxial growth temperature T _L of the light emitting layer 104 is 825 ° C., since the epitaxial growth temperature T _n of the n-side layer is 1075 ° C., T _n -T _L is 250 ° C.. When the epitaxial growth temperature T _p of the p-side layer is 1000 ° C., the T _n -T _p is less than or equal to 1/3 of the T _n -T _L at 75 ° C.. When the epitaxial growth temperature T _p of the p-side layer is 1025 ° C., the T _n -T _p is less than or equal to 1/5 of the T _n -T _L at 50 ° C.. When the epitaxial growth temperature T _p of the p-side layer is 1050 ℃, T _n -T _p is 1/8 or less of T _n -T _L at 25 ° C.. This means that the crystallinity of the p-side layer is improved and the emission intensity is improved by epitaxially growing the p-side layer at the same temperature as the n-side layer. The technical reason for this phenomenon is considered to be the ideal injection of holes from the p layer to the light emitting layer by improving the crystallinity of the p layer.

  The present invention is suitable for a light emitting element having a short wavelength in which an emission wavelength exists in the ultraviolet region. Short-wavelength light-emitting elements can be used for fluorescent lamps as well as photochemical fields using photoexcitation catalysts, lighting fields used to excite phosphors, bio-related fields such as kidnapping lights, and black lights. it can.

Sectional drawing of the semiconductor light-emitting device 1000 which concerns on the Example of this invention. The graph which shows the growth temperature of p side layer, and the relationship of emitted light intensity.

Explanation of symbols

1000: Semiconductor light emitting device 100: Sapphire substrate 101: Buffer layer 102: n-type contact layer 103: n layer 104: single quantum well light emitting layer (SQW)
105: p-type block layer 106: p-type contact layer 110: translucent thin film p-electrode 120: p-electrode 130: protective film 140: n-electrode 150: reflective metal layer

Claims (7)

In a method for manufacturing a light emitting device formed by stacking group III nitride compound semiconductors by epitaxial growth,
A growth temperature T _L (however, 800 ° C. or higher) of a light emitting layer that substantially contributes to light emission and contains at least indium (In) in its composition;
A growth temperature T _n of the n-type semiconductor layer in contact with the light emitting layer;
The growth temperature T _p of the p-type semiconductor layer in contact with the light emitting layer is
0 <T _n −T _p ≦ (T _n −T _L ) / 3
A method for producing a group III nitride compound semiconductor light-emitting device, characterized by comprising: In a method for manufacturing a light emitting device formed by stacking group III nitride compound semiconductors by epitaxial growth,
A growth temperature T _L (however, 800 ° C. or higher) of a light emitting layer that substantially contributes to light emission and contains at least indium (In) in its composition;
A growth temperature T _n of the n-type semiconductor layer in contact with the light emitting layer;
The growth temperature T _p of the p-type semiconductor layer in contact with the light emitting layer is
0 <T _n −T _p ≦ (T _n −T _L ) / 4
A method for producing a group III nitride compound semiconductor light-emitting device, characterized by comprising: In a method for manufacturing a light emitting device formed by stacking group III nitride compound semiconductors by epitaxial growth,
A growth temperature T _L (however, 800 ° C. or higher) of a light emitting layer that substantially contributes to light emission and contains at least indium (In) in its composition;
A growth temperature T _n of the n-type semiconductor layer in contact with the light emitting layer;
The growth temperature T _p of the p-type semiconductor layer in contact with the light emitting layer is
0 <T _n −T _p ≦ (T _n −T _L ) / 5
A method for producing a group III nitride compound semiconductor light-emitting device, characterized by comprising: 4. The III according to claim 1, wherein at least the light emitting layer, the n-type semiconductor layer, and the p-type semiconductor layer are formed by metal organic vapor phase epitaxy. A method for manufacturing a group nitride compound semiconductor light emitting device. 5. The method for producing a group III nitride compound semiconductor light-emitting element according to claim 1, wherein the temperature T _p is 1000 ° C. or higher. The method for producing a group III nitride compound semiconductor light-emitting device according to any one of claims 1 to 5, wherein a peak of an emission wavelength of the light-emitting layer is 380 nm or less. The method for manufacturing a group III nitride compound semiconductor light-emitting device according to any one of claims 1 to 6, wherein the light-emitting layer is a single quantum well or a multiple quantum well.

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