JP3468644B2 - Group III nitride semiconductor light emitting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a group III nitride semiconductor light emitting device which emits light in a purple or ultraviolet region (wavelength of 430 nm or less) with improved luminous efficiency.

[0002]

2. Description of the Related Art Hitherto, a light emitting device having a light emitting layer made of a Group III nitride semiconductor that emits light in a purple or ultraviolet region has been known. In addition, the light emitting device includes n ⁺ -doped silicon (Si) under the light emitting layer.
-GaN n-clad layer, p-Al _x1 Ga doped with magnesium (Mg) on the top of the light emitting layer
_1-x1 N p-cladding layer, where x1 <0.08,
It is constituted by a p-GaN contact layer on the p-clad layer.

[0003]

However, in the p-contact layer and the p-cladding layer, magnesium (Mg) forms a deep level acceptor level. The band gap between the deep level and the conduction band absorbs light having a wavelength of 430 nm or less. Therefore, in the above structure, when light having a wavelength of 430 nm or less is emitted from the light emitting layer, a part of the light emitted from the upper portion is absorbed by the p-contact layer and the p-clad layer, resulting in a weak emission output. There is. Therefore, it is an object of the present invention to increase the emission intensity by minimizing the absorption of light in the layer above the light emitting layer.

[0004]

[Means for Solving the Problems]
Therefore, the invention of claim 1 is made of a group III nitride semiconductor.Wavelength
Emits light of 430 nm or lessOf the light emitting layer and the light emitting layer
In a light emitting device having a p-clad layer formed on the top
The p-cladding layer is, With a thickness of 1 to 70 nm,
Magnesium (Mg) with 0.08 ≦ x1 ≦ 0.3
Loop Al_x1Ga_1-x1Made up of NA wave of light that absorbs and absorbs
With a layer whose length is shifted to the shorter wavelength side than the emission wavelengthSpecial to be
Group III nitride semiconductor light emitting deviceIs.

According to a second aspect of the present invention, the thickness of the p-contact layer made of magnesium (Mg) -doped GaN formed on the p-clad layer of the group III nitride semiconductor light emitting device according to the first aspect is set. The feature is that the thickness is 10 to 100 nm or less.

The invention of claim 3 relates to claim 1 or claim 2.
The n-clad layer formed under the light emitting layer of the group III nitride semiconductor light emitting device according to claim 1, is made of silicon (Si) -doped n ⁺ -Al _x2 Ga _{1 -x2} N having 0 <x2 ≦ 0.3. It is characterized by

The invention of claim 4 relates to claim 1 to claim 3.
The group III nitride semiconductor light-emitting device according to any one of 1 to 3, wherein a reflective film is provided on the back surface of the sapphire substrate. Further, the invention of claim 5 is characterized in that the reflecting film according to claim 4 is aluminum.

[0008]

According to the present invention, the p-clad layer of the group III nitride semiconductor light emitting device has a thickness of 1 to 70.
It is characterized by comprising magnesium (Mg) -doped Al _x1 Ga _1-x1 N with 0.08 ≦ x1 ≦ 0.3 in nm . As a result, conventional x1 <0.08 Al
spread the band gap than that of the _x1 Ga _1-x1 N,
Deep levels of magnesium (Mg) and Al _x1
Since the band gap with the Ga _{1 -x1} N conduction band also widens, the wavelength of the absorbed light becomes shorter. Furthermore, the film thickness is 70
Since the thickness is as thin as nm or less, the amount of light absorption is small. That is, the wavelength of the light absorbed by the p-clad layer is set to 43
Since the wavelength is shifted to the shorter wavelength side than 0 nm and the film thickness is made thin, as a result, the light absorbed when the light of 430 nm or less is emitted from the light emitting layer can be minimized,
The light emission output can be increased.

Further, as described in claim 2, the thickness of the p-contact layer of the group III nitride semiconductor light emitting device according to claim 1 is set to 10 to 100 nm , whereby a layer absorbing light of 430 nm or less is obtained. Becomes thinner, the amount of light absorbed decreases and the emission intensity increases.

According to a third aspect of the present invention, the n-clad layer of the group III nitride semiconductor light emitting device according to the first or second aspect is composed of silicon (Si) -doped n ⁺ -AlGaN. . This allows conventional silicon (Si)
Since the bandgap is wider than that of doped n ⁺ -GaN, light having a wavelength of 430 nm or less is not absorbed. Therefore, the emission intensity is increased.

According to a fourth aspect of the present invention, a reflective film is provided on the back surface of the sapphire substrate of the group III nitride semiconductor light emitting device according to any one of the first to third aspects. As shown, when the reflective film of the group III nitride semiconductor light emitting device according to claim 4 is made of aluminum, the light directed to the lower part of the light emitting layer can be reflected by the reflective film to emit light from the upper part. Therefore, the emission intensity of the light emitted from the upper portion increases.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on specific embodiments. The present invention is not limited to the examples below. FIG. 1 shows an overall view of a light emitting device 100 of this embodiment. The light emitting device 100 has a sapphire substrate 1, and 50 nm of Al on the sapphire substrate 1.
The N buffer layer 2 is formed. An aluminum reflection film 10 having a thickness of 200 nm is formed below the sapphire substrate 1.

On the buffer layer 2, a silicon (Si) -doped n film having a film thickness of 5.0 μm, an electron concentration of 1 × 10 ¹⁸ / cm ³ and a silicon concentration of 4 × 10 ¹⁸ / cm ³ is sequentially formed.
⁺ -Al _0.08 Ga _0.92 N with a high carrier concentration n-clad layer 3, a barrier layer made of GaN and silicon (Si) having a total film thickness of about 410 nm and silicon (Si) of 5 × 10 ¹⁸ / cm 3.
In _0.0 7 ^Ga 0.93 added at a concentration of ^{3
Light-emitting layer 4 having a multiple quantum well structure composed of well layers composed of N}
P-clad layer 5 composed of magnesium (Mg) -doped Al _0.08 Ga _0.92 N having ^{a film thickness of 50 nm, a hole concentration of 5 ×} 10 ¹⁷ / cm ³ , and a magnesium (Mg) concentration of 5 × 10 ²⁰ / cm ^3. Thickness 30nm, hole concentration 7x
10 ¹⁸ / cm ³ , magnesium (Mg) concentration 5 × 10
^A p-contact layer 6 made of ²¹ / cm ³ of magnesium (Mg) -doped GaN is formed. And p
A transparent electrode 8 made of a Ni / Au double layer is formed on the entire upper surface of the contact layer 6, and a pad 9 for bonding made of a Ni / Au double layer is formed at a corner of the transparent electrode 8; There is. An electrode 7 made of Al is formed on the n-clad layer 3.

As shown in FIG. 2, the detailed structure of the light emitting layer 5 is 21 barrier layers 41 made of GaN having a film thickness of 10 nm.
And silicon (Si) with a film thickness of 10 nm is 5 × 10 ¹⁸ / c
In _0.07 Ga _0.93 added at a concentration of m ^3.
It has a multiple quantum well structure in which 20 well layers 42 made of N are alternately stacked, and the total film thickness is about 410 nm.

Next, a method of manufacturing a semiconductor device having this structure will be described. The light emitting device 100 was manufactured by vapor phase growth by a metal organic vapor phase epitaxy method (hereinafter, MOVPE). The gas used is ammonia (NH ₃ ), carrier gas H ₂ or N ₂ , trimethylgallium (Ga (C 3
H _{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, the single crystal sapphire substrate 1 is MOVPE with the main surface being the surface cleaned by organic cleaning and heat treatment.
It is attached to the susceptor placed in the reaction chamber of the device. next,
The sapphire substrate was baked at a temperature of 1100 ° C. while flowing H ₂ into the reaction chamber at a flow rate of ₂ liter / minute for about 30 minutes under normal pressure.

Next, the temperature is lowered to 400 ° C., and H
₂ or N ₂ at 10 liter / min, NH ₃ at 10 lit / min
er / min, TMA 1.8 × 10 ⁻⁵ mol / min of about 90
It was supplied for 2 seconds to form the AlN buffer layer 2 with a thickness of about 50 nm. Next, the temperature of the sapphire substrate 1 is set to 1100.
Hold at 20 ° C., H ₂ at 20 liter / min, NH ₃ at 10
liter / min, TMA 0.47 × 10 ⁻⁴ mol /
Min., 1.12 × 10 ⁻⁴ mol / min of TMG, and silane (SiH ₄ ) diluted to 0.86 ppm with H ₂ gas at 2 × 10 ⁻⁷ mol / min for 100 min to introduce a film thickness of 5. 0μ
m, electron concentration 1 × 10 ¹⁸ / cm ³ , silicon concentration 4 ×
10 ¹⁸ / cm ³ silicon (Si) -doped Al
_A high carrier concentration n-clad layer 3 made of _0.08 Ga _0.92 N was formed.

After that, the temperature of the sapphire substrate 1 is set to 850.
Hold at 20 ° C., H ₂ at 20 liter / min, NH ₃ at 10
liter / min, TMG was introduced at 1.7 × 10 ⁻⁴ mol / min for 3 minutes to form a barrier layer 41 made of GaN and having a thickness of 10 nm. Then, add H ₂ to 20 liter / min, N
H ₃ at 10 liter / min, TMG at 2.1 × 10 ^-4
Mol / min, TMI 0.02 × 10 ⁻⁴ mol / min, H ₂
Silane (SiH diluted to 0.86 ppm by gas)
₄ ) is introduced at 10 × 10 ⁻⁸ mol / min for 3 minutes, and a thickness of In _0.07 Ga _0.93 N in which silicon (Si) is added at a concentration of 5 × 10 ¹⁸ / cm ³ 10n
m well layer 42 was formed. By repeating such a procedure, as shown in FIG. 2, the light emitting layer 4 having a multiple quantum well structure in which the barrier layer 41 and the well layer 42 are alternately laminated by 21 layers and 20 layers and the total film thickness is 410 nm is obtained. Formed.

Subsequently, the temperature was maintained at 1100 ° C., and H ₂
Or 10 liter / min of N ₂ and 10 liter of NH ₃
r / min, TMA 0.47 × 10 ⁻⁴ mol / min, TMG
1.12 × 10 ⁻⁴ mol / min, Cp ₂ Mg 2 × 10
^{-Introduced at a rate of 5} mol / min for 0.5 minutes, a film thickness of about 50 nm, and a magnesium (Mg) concentration of 5 x 10 ²⁰ / cm ^{3 made} of magnesium (Mg) -doped Al _0.08 Ga _0.92 N p- The clad layer 5 was formed. In this state, the p-cladding layer 5 is an insulator having a resistivity of 10 ⁸ Ωcm or more.

Next, the temperature was maintained at 1100 ° C., ₂₀ liters / minute of H ₂ or N _2, and 10 liters of NH ₃ .
/ Min, TMG 1.12 × 10 ⁻⁴ mol / min, Cp ₂ M
g at a rate of 2 × 10 ⁻⁵ mol / min for 0.5 minutes to obtain a film thickness of 3
0 nm, magnesium (Mg) concentration is 5 × 10 ²¹ / c
p − made of magnesium (Mg) -doped GaN of m ³
The contact layer 6 was formed. In this state, the p-contact layer 6 is an insulator having a resistivity of 10 ⁸ Ωcm or more.

Next, the p-contact layer 6 and the p-clad layer 5 were uniformly irradiated with an electron beam using an electron beam irradiation device. The electron beam irradiation conditions are an acceleration voltage of about 10 kV, a sample current of 1 μA, a beam moving speed of 0.2 mm / sec, a beam diameter of 60 μmφ, and a vacuum degree of 5.0 × 10 ⁻⁵ Torr. By this electron beam irradiation, the p-contact layer 6 and the p-clad layer 5 each have a hole concentration of 5 × 10 5.
¹⁷ / cm ³ , 7 × 10 ¹⁸ / cm ³ , resistivity 1 Ωc
It became a p-conduction type semiconductor of m and 0.7 Ωcm. In this way, a wafer having a multilayer structure was obtained.

Next, as shown in FIG. 3, a SiO ₂ layer 11 is sputtered on the p-contact layer 6 by sputtering.
It was formed to a thickness of 00 nm, and a photoresist 12 was applied on the SiO ₂ layer 11. Then, as shown in FIG. 3 by photolithography, on the p-contact layer 6, the photoresist 12 at the electrode formation site A ′ with respect to the n-clad layer 3 was removed. Next, as shown in FIG. 4, SiO not covered by the photoresist 12
_{The second} layer 11 was removed with a hydrofluoric acid-based etching solution.

Next, the p-contact layer 6, the p-clad layer 5, the light emitting layer 4, and the n-clad layer 3 which are not covered with the photoresist 12 and the SiO ₂ layer 11 are formed.
Vacuum degree 0.04 Torr, high frequency power 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, as shown in FIG. 5, a hole A for taking out an electrode from the n-clad layer 3 was formed. afterwards,
The photoresist 12 and the SiO ₂ layer 11 were removed.

Next, two layers of Ni / Au are uniformly vapor-deposited,
The transparent electrode 8 was formed on the p-contact layer 6 through a photoresist coating process, a photolithography process, and an etching process. Then, Ni is formed on part of the transparent electrode 8.
The pad 9 was formed by vapor-depositing two layers of / Au. On the other hand, n
-For the clad layer 3, aluminum was vapor-deposited to form the electrode 7.

Next, aluminum was evaporated to a thickness of 200 nm on the entire back surface of the sapphire substrate 1 to form the reflective layer 10. After that, the wafer treated as described above was cut into each element to obtain a light emitting diode having the structure shown in FIG. This light emitting device has a driving current of 20 mA and a peak light emission wavelength of 380
The emission intensity is 10 nm as compared with the conventional structure LED.
Doubled.

As described above, the present invention provides a Group III nitride semiconductor light emitting device that emits light in the violet and ultraviolet regions, with a p-clad layer containing magnesium (Mg) absorbing the light in the violet and ultraviolet regions. By reducing the thickness of the p-contact layer, the probability that light in the violet and ultraviolet regions is absorbed is reduced, and the luminous efficiency is increased. Also, p-
The luminous efficiency was increased by increasing the bandgap by increasing the mixed crystal ratio of aluminum in the clad layer so that light in the violet and ultraviolet regions was not absorbed. In addition, the n-clad layer is made of AlGaN instead of GaN to increase the band gap so that light in the violet and ultraviolet regions is not absorbed. Further, by forming a reflective film below the sapphire substrate, As a result that the light emitted to the lower part also emitted from the upper part, the emission intensity increased.

Although the light emitting layer has a multiple quantum well structure in the above embodiments, it may have a single quantum well structure or a bulk structure. The light emitting layer may be made of any group III nitride semiconductor other than GaN or InGaN as long as it can emit light in the violet and ultraviolet region of 430 nm or less. Further, in the above embodiment, only the well layer is doped with silicon. However, other donor impurities or acceptor impurities may be added to the well layer and / or the barrier layer as long as light in the violet and ultraviolet region of 430 nm or less can be emitted. May be.

Although the n-cladding layer is formed of one layer, it may be formed of two layers of an n layer and an n ⁺ layer.
Furthermore, the p-contact layer is also formed as a single layer,
It may be formed of two layers. Further, in the above embodiment, the electron beam irradiation is carried out when making the p-type, but it may be carried out by thermal annealing, heat treatment in N ₂ plasma gas, or laser irradiation.

In the above embodiment, the reflection film is made of aluminum, but it is light in the purple and ultraviolet regions.
The material is not limited to aluminum as long as it is a material that reflects light having a wavelength of 0 nm or less without absorbing it.

The silicon concentration of the n-clad layer 3 is 1 × 1.
0 ¹⁷ to 1 × 10 ²⁰ / cm ³ is desirable, and the electron concentration is preferably 1 × 10 ¹⁶ to 1 × 10 ¹⁹ / cm ³ . The film thickness is preferably 0.5 to 10 μm. If the silicon concentration is 1 × 10 ¹⁷ / cm ³ or less, the resistance becomes high and 1
It is not desirable for it to be not less than × 10 ²⁰ / cm ³ , because the crystallinity will decrease. Further, the electron concentration is 1 × 10 ¹⁶ / cm ³
When it is below, the series resistance of the light emitting element becomes high, and 1 × 10
^{If it is 19} / cm ³ or more, the crystallinity deteriorates, which is not desirable. When the film thickness is 10 μm or more, the substrate is curved, and when the film thickness is 0.5 μm or less, etching is performed to expose the n-clad layer 3 and it is difficult to form an electrode on the n-clad layer 3, which is not desirable. n-cladding layer 3
The Al mixed crystal ratio of AlGaN is preferably 0 to 30%,
A more desirable range is 0 to 15%. If it is 15% or less, the crystallinity becomes better, which is desirable.

The hole concentration of the p-clad layer 5 is 1 × 10.
^It is preferably ¹⁷ to 1 × 10 ¹⁸ / cm ³ . When the hole concentration is 1 × 10 ¹⁸ / cm ³ or more, the crystallinity is deteriorated, which is not desirable, and when the hole concentration is 1 × 10 ¹⁷ / cm ³ or less, the series resistance of the light emitting element becomes too high, which is not desirable. Further, the film thickness of the p-clad layer 5 is preferably 1 to 70 nm. If it is 70 nm or more, the effect is not so great, and if it is 1 nm or less, the carrier confinement effect is lowered, and the light emission efficiency is lowered, which is not desirable. AlGa of p-cladding layer 5
The mixed crystal ratio of N Al is preferably 8 to 30%. If it is 8% or less, it is not desirable because the bandgap is small and the absorption of light in the purple and ultraviolet regions is large at the magnesium (Mg) level of impurities. Undesired to.

The thickness of the p-contact layer 6 is 10 to 100.
The range of nm is desirable, and the range of 10 to 20 nm is desirable. A range of 10 to 20 nm is desirable because it reduces light absorption. Further, if it is 100 nm or more, the effect is not so great, and if it is 10 nm or less, the ohmic property with respect to the metal electrode is deteriorated, which is not desirable.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing a configuration of a light emitting layer of the light emitting diode according to the 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.

[Description of Reference Signs] 100 ... Light emitting diode 1 ... Sapphire substrate 2 ... Buffer layer 3 ... High carrier concentration n ⁺ layer 4 ... Light emitting layer 5 ... P-clad layer 6 ... P-contact layer 7 ... Electrode 8 ... Transparent electrode 9 ... Pad 10 ... Reflective film

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shiro Yamazaki               Aichi prefecture Kasuga-cho, Kasuga-cho               Address 1 Toyota Gosei Co., Ltd. (72) Inventor Toshio Hiramatsu               Aichi prefecture Kasuga-cho, Kasuga-cho               Address 1 Toyota Gosei Co., Ltd.                (56) Reference JP-A-8-32116 (JP, A)                 JP 59-18688 (JP, A)                 JP-A-63-301573 (JP, A)                 JP-A-8-236445 (JP, A)                 58-74356 (JP, U)

Claims (5)

(57) [Claims] 1. A formed Ri wavelength from group III nitride semiconductor 430n
A light emitting device having a light emitting layer that emits light of m or less and a p-clad layer formed on the light emitting layer, wherein the p-clad layer has a thickness of 1 to 70 nm, and
Magnesium (Mg) -doped A with 8 ≦ x1 ≦ 0.3
l _x1 Ga _1-x1 Ri from N formed, before the wavelength of the absorption light
A Group III nitride semiconductor light-emitting device, which is a layer shifted to a shorter wavelength side than the emission wavelength . 2. The Group 3 element according to claim 1, wherein the p-contact layer made of magnesium (Mg) -doped GaN formed on the p-clad layer has a thickness of 10 to 100 nm. Nitride semiconductor light emitting device. 3. An n-clad layer formed under the light emitting layer is silicon (Si) -doped n with 0 <x2 ≦ 0.3.
⁺ -Al _x2 Ga _1-x2 3-nitride semiconductor light emitting device according to claim 1 or claim 2, characterized in that it consists of N. 4. A light emitting device having a light emitting layer made of a Group 3 nitride semiconductor, comprising a sapphire substrate, and a reflective film provided on the back surface of the sapphire substrate. 3. The group III nitride semiconductor light emitting device according to any one of claims. 5. The Group III nitride semiconductor device according to claim 4, wherein the reflective film is aluminum.