JPH08125223A - Group iii nitride semiconductor light-emitting element and its manufacture - Google Patents

Abstract

PURPOSE: To improve the crystallizability of group III nitride semiconductor and to improve light emitting brightness by forming a buffer layer consisting of amorphous Alx Gay In1-x-y N: X+Y≠1 on a Sapphire substrate. CONSTITUTION: Amorphous buffer layer 2 consisting of Alx Gay In1-x-y N: X+Y≠1 with a thickness of 100-500 is formed on a Sapphire substrate 1 at 300-800 deg.C and group III nitride semiconductor (including Alx Gay In1-x-y N: X=0, Y=0, X=Y=0) is subjected to epitaxial growth on it at 800-1200 deg.C. Then, in a light- emitting diode 10, high-carrier concentration n<+> layers 3 and 4, p-type light emitting layer 5, p-layer 61, and second and first contact layers 62 and 63 are formed successively on the buffer layer 2, thus improving the blue light-emitting intensity of the group III nitride semiconductor light-emitting element by the epitaxial growth film of an improved nitride semiconductor (including Alx Gay In1-x-y N: X=0, Y=0, X=Y=0).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blue light emitting group III nitride semiconductor light emitting device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a blue light emitting diode, one using a GaN compound semiconductor has been known. Its GaN
Attention has been paid to the fact that the compound semiconductors of the type have high emission efficiency because they are direct transitions, and that blue, which is one of the three primary colors of light, is the emission color.

A light emitting diode using such a GaN compound semiconductor has a buffer layer made of aluminum nitride or gallium nitride on a sapphire substrate,
growing an n-layer made of n-type GaN-based compound semiconductor,
A p-type impurity is added on the n-layer to form a semi-insulating i-type
It has a structure in which an i layer made of a GaN-based compound semiconductor or a p-layer made of a p-type GaN-based compound semiconductor is grown by heat treatment or electron beam irradiation (JP-A-62-119196, JP-A-62-119196). 63-188977, JJAP Vol.30, No.12A, 199
Dec. 9, pp.L1998-L2008, JJAP Vol.31, Part2, No.2B,
February 1992, pp.L139-L142).

[0004]

However, the light emission intensity of the light emitting diode having the above structure is not yet sufficient, and improvement is desired. As a result of repeated studies, the inventors of the present invention have performed a good-quality Group III nitride semiconductor (Al _x Ga _Y In _1-XY N;
It was possible to obtain epitaxial growth films with X = 0, Y = 0, and X = Y = 0. As a result, the emission brightness was improved. The present invention solves this problem, and an object thereof is to improve blue light emission intensity.

[0005]

The present invention provides a sapphire substrate and a group III nitride semiconductor (Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y =
In a light emitting element having a light emitting portion composed of a plurality of layers each including (including 0), a temperature of 300
Amorphous Al _X Ga _Y In _1-XY N; X + Y ≠ ° C. to 800 ° C.
1 has a buffer layer formed to a thickness of 100Å to 500Å, and each layer of the light emitting portion is formed on the buffer layer.

Another invention is a group III nitride semiconductor (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0) on a sapphire substrate.
In a method of epitaxially growing a layer consisting of
Amorphous Al _X Ga _Y In with a thickness of 100Å to 500Å on a sapphire substrate at a temperature of 300 ° C to 800 ° C.
_A buffer layer composed of _1-XY N; X + Y ≠ 1 is grown, and a Group III nitride semiconductor (Al _x Ga _Y In _1-XY N; X = 0, at a temperature of 800 ° C. to 1200 ° C.) is grown on the buffer layer. (Including Y = 0 and X = Y = 0) is epitaxially grown.

[0007]

FUNCTION AND EFFECTS OF THE INVENTION As described above, the thickness of 100 Å on the sapphire substrate at the temperature of 300 ° C to 800 ° C.
~ 500Å Al _X Ga _Y In _1-XY N; X + Y ≠ 1 was formed, and as a result, the group III nitride semiconductor (Al _x Ga _Y In _{1- XY} N; X = 0, Y = 0, X =
The crystallinity of (including Y = 0) could be improved. As a result, the emission brightness of the light emitting element was improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a light emitting diode 10 has a sapphire substrate 1 on which the sapphire substrate 1 is mounted.
A buffer layer 2 of Al _0.1 Ga _0.83 In _0.07 N of 500 Å is formed. A film thickness of about 2.0 is formed on the buffer layer 2 in order.
[mu] m, the electron concentration of 2 × 10 ¹⁸ / cm high carrier concentration comprising a silicon-doped GaN of ³ n ⁺ layer 3, a thickness of about 2.0 [mu] m, the electron concentration of 2 × 10 ¹⁸ / cm ³ of silicon-doped (Al _x2 Ga _{1- x2} ) _y2 In
High carrier concentration n ⁺ layer 4 consisting of _1-y2 N, film thickness about 0.5 μ
m, magnesium (Mg), cadmium (Cd) and silicon-doped (Al _x1 Ga _1-x1 ) _y1 In _1-y1 N p-conductivity type light-emitting layer 5, film thickness about 1.0 μm, hole concentration 5 × 10 ¹⁷ / cm ³ , magnesium concentration 1 × 10 ²⁰ / cm ³ magnesium-doped (Al
_x2 Ga _1-x2 ) _y2 In _1-y2 N p-layer 61, film thickness about 0.2 μ
m, hole concentration 5 × 10 ¹⁷ / cm ³ , magnesium concentration 1 × 10
²⁰ / cm ³ second contact layer 62 made of magnesium-doped GaN, film thickness of about 500Å, hole concentration 2 × 10 ¹⁷ / cm ³ ,
Magnesium concentration of 2 × 10 ²⁰ / cm ³
A first contact layer 63 made of GaN is formed.
Then, an electrode 7 made of nickel and connected to the first contact layer 63 and an electrode 8 made of nickel and connected to the high carrier concentration n ⁺ layer 4 are formed. The electrode 7 and the electrode 8 are electrically insulated and separated by the groove 9.

Next, a method of manufacturing the light emitting diode 10 having this structure will be described. The light emitting diode 10 is
It was manufactured by vapor phase growth by an organometallic compound vapor phase growth method (hereinafter referred to as “M0VPE”). The gas used was NH
₃ and carrier gas H ₂ or N ₂ and trimethylgallium (Ga
(CH _{3) 3)} and (hereinafter referred to as "TMG") and trimethylaluminum (Al (CH _{3) 3)} (hereinafter referred to as "TMA") and trimethyl indium (an In (CH _{3) 3)} (hereinafter "TMI" Dimethyl cadmium (Cd (CH ₃ ) ₂ ) (hereinafter referred to as “DMCd”), silane (SiH ₄ ) and cyclopentadienyl magnesium (Mg
(C ₅ H ₅ ) ₂ ) (hereinafter referred to as “CP ₂ Mg”).

First, a single crystal sapphire substrate 1 having an a-plane as a main surface, which has been cleaned by organic cleaning and heat treatment, is mounted on a susceptor placed in a reaction chamber of a M0VPE apparatus. Then, at a pressure of 1100 while flowing H ₂ into the reaction chamber at a flow rate of 2 liter / min under normal pressure
The sapphire substrate 1 was vapor-phase etched at 0 ° C.

Next, the temperature is lowered to 400 ° C. and H ₂ is added.
20 liter / min, NH ₃ 10 liter / min, TMA 1.8 × 10 ^-5
Mol / min, TMG 1.5 × 10 ^-4 mol / min, TMI 1.3 × 10
A buffer layer 2 of Al _0.1 Ga _0.83 In _0.07 N was formed at a thickness of about 500 Å by supplying at ⁻⁵ mol / min. Then, maintaining the temperature of the sapphire substrate 1 to 1150 ° C., to form a film thickness of about 2.2 [mu] m, an electron concentration of 2 × 10 ¹⁸ / cm high carrier concentration n ⁺ layer 3 made of GaN of silicon doped ^3.

Hereinafter, the light emitting layer 5 (active layer) and the high carrier concentration n ⁺ layer 4 and the p layer which are the cladding layers when the emission peak wavelength is set to 430 nm with cadmium (Cd) and silicon (Si) as the emission centers. An example of the composition ratio of 61 and crystal growth conditions will be described. After forming the above-mentioned high carrier concentration n ⁺ layer 3, the temperature of the sapphire substrate 1 is kept at 850 ° C., N ₂ or H ₂ is 10 liter / min, and NH ₃ is 10 liter / min.
Min, TMG 1.12 × 10 ^-4 mol / min, TMA 0.47 × 10 ^-4 mol / min, TMI 0.1 × 10 ^-4 mol / min, and silane introduced, film thickness about 0.5 μm, concentration 1 A high carrier concentration n ⁺ layer 4 made of (Al _0.47 Ga _0.53 ) _0.9 In _0.1 N doped with silicon of × 10 ¹⁸ / cm ³ was formed.

Subsequently, the temperature was maintained at 850 ° C. and N ₂ or H _{2 was} added.
20 liter / min, NH ₃ 10 liter / min, TMG 1.53 × 10
^-4 mol / min, TMA 0.47 × 10 ^-4 mol / min, TMI 0.02 ×
10 ^-4 mol / min and CP ₂ Mg at 2 × 10 ^-4 mol / min and DMCd
Of 2 × 10 ^-7 mol / min and silane of 10 × 10 ^-9 mol / min were introduced, and magnesium (Mg) and cadmium (C
A light emitting layer 5 composed of d) and silicon (Si) -doped (Al _0.3 Ga _0.7 ) _0.94 In _0.06 N was formed. In this state, the light emitting layer 5 still has high resistance. Magnesium in this light emitting layer 5
The concentration of (Mg) is 1 × 10 ¹⁹ / cm ³ , the concentration of cadmium (Cd) is 5
× 10 ¹⁸ / cm ³ and the concentration of silicon (Si) is 1 × 10 ¹⁸ / cm ³
Is.

Subsequently, the temperature was maintained at 1100 ° C. and N ₂ or H _{2 was} added.
20 liter / min, NH ₃ 10 liter / min, TMG 1.12 × 10
^-4 mol / min, TMA 0.47 × 10 ^-4 mol / min, TMI 0.1 ×
10 ^-4 mol / min, and, CP to ₂ Mg 2 × 10 ^-4 mol / min was introduced, a film thickness of about 1.0 [mu] m of magnesium (Mg) doped (Al
_A p-layer 61 made of _0.47 Ga _0.53 ) _0.9 In _0.1 N was formed.
The concentration of magnesium in the p-layer 61 is 1 × 10 ²⁰ / cm ³ .
In this state, the p layer 61 is still an insulator having a resistivity of 10 ⁸ Ωcm or more. Next, the temperature is maintained at 850 ° C and N ₂ or
H ₂ 20 liter / min, NH _{3 10} liter / min, TMG 1.12 ×
Introducing 10 ⁻⁴ mol / min and CP ₂ Mg at a rate of 2 × 10 ⁻⁴ mol / min, and doping with magnesium (Mg) having a film thickness of about 0.2 μm.
A second contact layer 62 made of GaN was formed. The magnesium concentration of the second contact layer 62 is 1 × 10 ²⁰ / cm ³ . In this state, the second contact layer 62 still has
It is an insulator with a resistivity of 10 ⁸ Ωcm or more. Then, set the temperature to 85
Hold at 0 ℃, N ₂ or H ₂ 20 liter / min, NH ₃ 10 lit
er / min, TMG 1.12 × 10 ^-4 mol / min, and CP ₂ Mg 4
Introduced at a rate of × 10 ^-4 mol / min, the first contact layer 63 made of GaN doped with magnesium (Mg) and having a film thickness of about 500 Å
Was formed. The concentration of magnesium in the first contact layer 63 is 2 × 10 ²⁰ / cm ³ . In this state, the first contact layer 63 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.

Next, using a backscattered electron diffraction apparatus, the first
The contact layer 63, the second contact layer 62, the p layer 61, and the light emitting layer 5 were uniformly irradiated with an electron beam. The electron beam irradiation conditions are: accelerating voltage of about 10 KV, sample current of 1 μA, beam moving speed of 0.2 mm / sec, beam diameter of 60 μmφ, vacuum degree of 5.0 × 10 ^-5.
Torr. By this electron beam irradiation, the first contact layer 63, the second contact layer 62, the p layer 61 and the light emitting layer 5 are formed.
Are hole concentration 2 × 10 ¹⁷ / cm ³ and 5 × 10 ¹⁷ / c, respectively.
m ³ , 5 × 10 ¹⁷ / cm ³ , resistivity 2 Ωcm, 0.8 Ωcm, 0.8 Ωcm
Became a p-conduction type semiconductor. In this way, a wafer having a multilayer structure as shown in FIG. 2 was obtained.

FIGS. 3 to 7 described below are cross-sectional views showing only one device on the wafer. In actuality, processing is performed on a wafer in which this device is continuously repeated. It is cut for each element.

As shown in FIG. 3, the first contact layer 63
An SiO ₂ layer 11 having a thickness of 2000 Å was formed on the above by sputtering. Next, a photoresist 12 was applied on the SiO ₂ layer 11. And by photolithography,
On the first contact layer 63, a high carrier concentration n ⁺
The photoresist of the electrode forming portion A corresponding to the hole 15 formed to reach the layer 4 and the portion B forming the groove 9 for insulatingly separating the electrode forming portion from the electrode of the p layer 61 was removed.

Next, as shown in FIG. 4, the SiO ₂ layer 11 not covered with the photoresist 12 was removed with a hydrofluoric acid type etching solution. Next, as shown in FIG.
Part of the upper surface of the p layer 6 and the light emitting layer 5 thereunder, which is not covered with the photoresist 12 and the SiO ₂ layer 11, and the high carrier concentration n ⁺ layer 4, a vacuum degree of 0.04 Torr and a high frequency power of 0.
44 W / cm ² and BCl ₃ gas were supplied at a rate of 10 ml / min to perform dry etching, and then dry etching was performed using Ar. In this step, a hole 15 for taking out an electrode and a groove 9 for insulating separation were formed for the high carrier concentration n ⁺ layer 4.

Next, as shown in FIG. 6, the SiO ₂ layer 11 remaining on the p layer 61 was removed with hydrofluoric acid. next,
As shown in FIG. 7, a Ni layer 13 was formed on the entire surface of the sample by vapor deposition. As a result, the Ni layer 13 electrically connected to the high carrier concentration n ⁺ layer 4 is formed in the hole 15. Then, as shown in FIG. 7, a photoresist 14 is applied on the Ni layer 13, and the photoresist 14 is formed into a high carrier concentration n ⁺ layer 4 by photolithography.
A pattern was formed in a predetermined shape so that the electrode portion for the p-layer 61 and the p-layer 61 remained.

Next, as shown in FIG. 7, the exposed portion of the lower Ni layer 13 was etched with a nitric acid-based etching solution using the photoresist 14 as a mask. At this time, the Ni layer 13 deposited in the groove 9 for insulation separation is completely removed.
Next, the photoresist 14 was removed with acetone, and the electrode 8 of the high carrier concentration n ⁺ layer 4 and the electrode 7 of the first contact layer 63 were left. After that, the wafer treated as described above was cut into each element to obtain the gallium nitride-based light emitting element having the ppn structure shown in FIG.

The light emitting device thus obtained had a driving current of 20 mA, a driving voltage of 4 V, an emission peak wavelength of 430 nm and an emission intensity of 1 cd.

Further, cadmium (C
The concentrations of d) and silicon (Si) are 1 × 10 ¹⁷ to 1 respectively.
The range of × 10 ²⁰ is desirable from the viewpoint of improving the emission intensity.
The concentration of silicon (Si) is higher than that of cadmium (Cd).
It is more preferable that the amount is as small as 1/2 to 1/10.

In the above-mentioned embodiment, the p layer 6 and the high carrier concentration n ⁺ layer 4 in which the band gap of the light emitting layer 5 exists on both sides.
Is formed in a double heterojunction that is smaller than the band gap. Also, these three layers of Al and G
The component ratios of a and In are selected so as to match the lattice constant of the high carrier concentration n ⁺ layer of GaN.

In the above embodiment, the buffer layer 2 is made of Al _0.1 G.
Although it was composed of a _0.83 In _0.07 N, the AlGaInN-based semiconductor crystal formed on it with the other composition ratios was of good quality. or,
Although the method of forming by MOCVD has been described in the above embodiment, the buffer layer 2 and the semiconductor crystal thereon can be formed with good quality even in MOVPE.

In the above embodiment, the concentrations of zinc (Zn) and silicon (Si) in the light emitting layer 5 are 1 × 10 5, respectively.
It was found that the range of ¹⁷ to 1 × 10 ²⁰ is desirable in terms of improving the emission intensity. More preferably 1 × 10 ¹⁸ to 1 ×
A range of 10 ¹⁹ is good. If it is less than 1 × 10 ¹⁸ , the effect is small, and if it is more than 1 × 10 ¹⁹ , the crystallinity deteriorates. Further, the concentration of silicon (Si) is preferably 10 times to 1/10 that of zinc (Zn), more preferably about 1 to 1/10 or less.

Further, in the above-mentioned embodiment, the first contact layer 63 to which magnesium (Mg) is added at a high concentration and the first contact layer 63 to which magnesium (Mg) is added at a lower concentration than the first contact layer 63 are used as the contact layer. It has a two-layer structure with two contact layers 62. However, magnesium (Mg) of p layer 5
Only one contact layer having a magnesium (Mg) concentration higher than the concentration may be provided immediately below the electrodes 7 and 8. Although GaN is used as the contact layer, a mixed crystal having the same composition ratio as the p layer 5 may be used.

The acceptor impurities are beryllium (B
You may use e), magnesium (Mg), zinc (Zn), cadmium (Cd), and mercury (Hg). Further, donor impurities include carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead.
(Pb) can be used.

Further, sulfur (S) is used as a donor impurity.
, Selenium (Se) and tellurium (Te) can also be used. p
Molding can be performed by electron beam irradiation, thermal annealing, heat treatment in N ₂ plasma gas, or laser irradiation.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a first specific example of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of the light emitting diode of the same embodiment.

FIG. 3 is a cross-sectional view showing a manufacturing process of the light emitting diode of the embodiment.

FIG. 4 is a cross-sectional view showing a manufacturing process of the light emitting diode of the same embodiment.

FIG. 5 is a cross-sectional view showing the manufacturing process of the light emitting diode of the same embodiment.

FIG. 6 is a cross-sectional view showing a manufacturing process of the light emitting diode of the embodiment.

FIG. 7 is a sectional view showing a manufacturing process of the light emitting diode of the embodiment.

[Explanation of symbols]

10 ... Light emitting diode 1 ... Sapphire substrate 2 ... Buffer layer 3 ... High carrier concentration n ⁺ layer 4 ... High carrier concentration n ⁺ layer 5 ... Light emitting layer 61 ... P layer 62 ... Second contact layer 63 ... First contact layer 7, 8 ... Electrode 9 ... Groove

Claims (2)

[Claims] 1. A sapphire substrate and a Group III nitride semiconductor (A
l _x Ga _Y In _1-XY N; X = 0, Y = 0, including X = Y = 0) in a light-emitting element having a plurality of layers, wherein on the sapphire substrate, At a temperature of 300 ° C to 800 ° C, amorphous Al _X Ga _Y In _1-XY N; X + Y ≠ 1 has a thickness of 100Å
A group III nitride semiconductor light emitting device having a buffer layer formed to a thickness of about 500 Å, and forming each layer of the light emitting unit on the buffer layer. 2. A group III nitride semiconductor (A) on a sapphire substrate.
L _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0) is epitaxially grown on the sapphire substrate at a temperature of 300 ° C to 800 ° C. 100 Å ~ 500 Å amorphous Al _X Ga _Y In
_A buffer layer composed of _1-XY N; X + Y ≠ 1 is grown, and a Group III nitride semiconductor (Al _x Ga _Y In _1-XY N; X = 0, at a temperature of 800 ° C. to 1200 ° C.) is grown on the buffer layer. Y = 0, X = Y = 0) are epitaxially grown.