JPH07297447A - Group iii nitride semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To increase the luminous intensity of a light emitting element by adding magnesium and zinc to the light emitting layer of the element as impurities. CONSTITUTION:A light emitting diode 10 has a sapphire substrate 1 and an AlN buffer layer 500Angstrom thick is formed on the substrate 1. Then a high carrier concentration n<+>-type layer 3 composed of Si-doped GaN, high carrier concentration N<+>-type-layer 4 composed of Si-doped (Alx2Ga1-x2)y2In1-y2N, light emitting- layer 5 composed of Zn- and Mg-doped (Alx1Ga1-x1)y1In1-y1N, and p-type layer 6 composed of Mg-doped (Alx2Ga1-x2)y2In1-y2N are successively formed on the buffer layer 2. Then a nickel electrode 7 to be connected to the p-type layer 6 and another nickel electrode 8 to be connected to the n-type layer 4 are formed. The electrodes 7 and 8 are electrically isolated and separated from each other by a groove 9. Since the diode 10 emits light by utilizing the transition between levels having high transition probabilities, the luminous intensity of the diode 10 is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device using a group III nitride semiconductor.

[0002]

2. Description of the Related Art Conventionally, as a blue light emitting diode, one using a pn junction of a GaN compound semiconductor is known. Since the compound semiconductor is a direct transition type, it has been noted that it has high emission efficiency, and that blue, which is one of the three primary colors of light, is used as the emission color.

In the above light emitting device, the p layer is formed by irradiating an electron beam after doping GaN with magnesium (Mg).

[0004]

However, the above-mentioned light emitting device has an advantage that the operating voltage is lower than that of the MIS type light emitting device using the semi-insulating semiconductor layer, but it still emits light. The strength is low. The emission mechanism of this device is due to the transition between the conduction band and the acceptor level of magnesium, but due to the large energy level difference, non-radiative recombination via other deep levels is predominant. Therefore, it seems that the emission intensity is not high. The peak wavelength is 43
It is in the vicinity of 0 nm, and is slightly shifted to the short wavelength side with respect to pure blue. The present invention has been made to solve the above problems, and an object thereof is to improve the light emission intensity of a light emitting element using an AlGaInN semiconductor and obtain a spectrum closer to pure blue.

[0005]

The invention according to claim 1 is a group III nitride semiconductor (Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0).
The three layers in which the n layer showing the n-conduction type, the p layer showing the p-conduction type, and the light-emitting layer interposed therebetween are formed by a monojunction, a single heterojunction, or a double heterojunction. In the light emitting device having a structure, magnesium (Mg) and zinc (Zn) are added as impurities to the light emitting layer. The invention according to claim 2 uses a group III nitride semiconductor (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0) to show n-conductivity type. In a light emitting device having an n layer and a light emitting layer exhibiting a p-conduction type, the light emitting layer is made of magnesium (Mg)
And a zinc (Zn) are added as impurities. Magnesium (Mg) has a concentration of 1 × 10 ¹⁸
~ 1 × 10 ²⁰ / cm ³ , zinc (Zn) concentration 1 × 10 ¹⁸ ~ 1 × 10
It is desirable that it is added at ²⁰ / cm ³ . According to a fifth aspect of the invention, the light emitting layer is formed by a thin film multi-layer in which a thin film to which magnesium (Mg) is added and a thin film to which zinc (Zn) is added are repeated.

[0006]

The acceptor level formed in the light-emitting layer is deeper in the valence band of zinc (Zn) than that of magnesium (Mg). Therefore, the transition between the conduction band with a small level difference and the acceptor level of zinc (Zn) is more dominant than the transition between the conduction band with a large level difference and the acceptor level of Magnesium (Mg). Becomes Therefore, the light emission is due to the transition between levels having a high transition probability, the emission intensity is improved, and the peak wavelength is shifted to the long wavelength side, and the light emission is closer to pure blue.

[0007]

First Embodiment Referring to FIG. 1, a light emitting diode 10 has a sapphire substrate 1 on which 500 Å of Al is placed.
An N 2 buffer layer 2 is formed. Its buffer layer 2
On the top, in order, a film thickness of about 2.0 μm, electron concentration 2 × 10 ¹⁸ / c
High carrier concentration n ⁺ layer 3 consisting of m ³ silicon-doped GaN, thickness of about 2.0 μm, electron concentration of 2 × 10 ¹⁸ / cm ³ of silicon-doped (Al _x2 Ga _1-x2 ) _y2 In _1-y2 N Consisting of a high carrier concentration n ⁺ layer 4, a film thickness of about 0.5 μm, a light emitting layer 5 composed of zinc- and magnesium-doped (Al _x1 Ga _1-x1 ) _y1 In _1-y1 N, a film thickness of about 1.0 μm, a hole concentration of 2 × A p-layer 6 of 10 ¹⁷ / cm ³ of magnesium-doped (Al _x2 Ga _1-x2 ) _y2 In _1-y2 N is formed. Then, an electrode 7 made of nickel connected to the p layer 6 and an electrode 8 made of nickel 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 epitaxy by an organometallic compound vapor phase epitaxy method (hereinafter referred to as "M0VPE").

The gases used are NH ₃ and carrier gas H ₂
Or N ₂ and trimethyl gallium _{(Ga (CH 3) 3)} ( hereinafter "TMG"
) And trimethylaluminum (Al (CH ₃ ) ₃ ) (hereinafter referred to as “TMA”) and trimethylindium (In (CH ₃ ) ₃ ).
(Hereinafter referred to as “TMI”) and diethyl zinc ((C ₂ H ₅ ) ₂ Zn)
(Hereinafter, referred to as "DEZ") is a 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
The buffer layer 2 of AlN was formed at a thickness of about 500Å by supplying at a mol / min. Next, the temperature of the sapphire substrate 1 is set to 1150.
℃ to retain a thickness of about 2.2 [mu] m, the electron concentration of 2 × 10 ¹⁸ / cm high carrier concentration of GaN silicon doped ³ n ⁺ layer 3
Was formed.

An example of the composition ratio of the light emitting layer 5 (active layer) and the cladding layers 4 and 6 and the crystal growth conditions when the emission peak wavelength is set to 500 nm with zinc (Zn) as the emission center will be described below. After forming the above-mentioned high carrier concentration n ⁺ layer 3, the temperature of the sapphire substrate 1 is kept at 800 ° C., N ₂ is 20 liter / min, NH ₃ is 10 liter / min, and TMG is 1.
12 × 10 ^-4 mol / min, TMA 0.47 × 10 ^-4 mol / min, TMI
0.1 × 10 ⁻⁴ mol / min, and introducing silane, film thickness of about 0.
Silicon-doped (Al _0.3 Ga 5 μm, concentration 2 × 10 ¹⁹ / cm ³
_A high carrier concentration n ⁺ layer 4 composed of _0.7 ) _0.94 In _0.06 N was formed.

Subsequently, the temperature was maintained at 1150 ° C. and N ₂ was added to 20 l.
iter / 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 2 x 10 ^-7 mol / min, DEZ 2 x
10 ^-4 mol / min was introduced 7 minutes, doped magnesium having a thickness of about 0.5 μm (Mg) and zinc _{(Zn) (Al 0.09 Ga 0.91} ) 0. 99
A light emitting layer 5 made of In _0.01 N was formed. The light emitting layer 5 is still an insulator having a resistivity of 10 ⁸ Ωcm or more in this state. The concentration of magnesium (Mg) in this light emitting layer 5 is 1 × 10 ¹⁹ / c
m ³ and the concentration of zinc (Zn) is 2 × 10 ¹⁸ / cm ³ .

Subsequently, the temperature was maintained at 1100 ° C., and N ₂ was added at 20 l.
iter / 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 ₂ Mg Introduced at 2 × 10 ^-4 mol / min, magnesium (Mg) -doped (Al _0.3 Ga _0.7 ) with a film thickness of about 1.0 μm
_A p-layer 6 made of _0.94 In _0.06 N was formed. The concentration of magnesium in the p-layer 6 is 1 × 10 ²⁰ / cm ³ . In this state,
The p-layer 6 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.

Next, the reflection electron beam diffractometer was used to uniformly irradiate the light emitting layer 5 and the p layer 6 with an electron beam. The electron beam irradiation conditions are: accelerating voltage of about 10 KV, material current of 1 μA, beam moving speed of 0.2 mm / sec, beam diameter of 60 μmφ, vacuum degree of 5.0 ×
It is 10 ^-5 Torr. By the irradiation of this electron beam, the light emitting layer 5 and the p layer 6 became a p-conduction type semiconductor having a hole concentration of 2 × 10 ¹⁷ / cm ³ and a resistivity of 2 Ωcm. 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 element on the wafer. In fact, a wafer in which this element is continuously repeated is processed, and then each of the elements is processed. It is cut for each element.

As shown in FIG. 3, a SiO ₂ layer 11 having a thickness of 2000 Å was formed on the p layer 6 by sputtering.
Next, a photoresist 12 was applied on the SiO ₂ layer 11. Then, by photolithography, on the p layer 6, the electrode forming portion A corresponding to the hole 15 formed to reach the high carrier concentration n ⁺ layer 4 and the electrode forming portion are insulated and separated from the electrode of the p layer 6. The photoresist in the portion B where the groove 9 is formed 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 6 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, a photoresist 14 is applied on the Ni layer 13, and the photoresist 1 is applied by photolithography.
4 was patterned into a predetermined shape so that the electrode portions for the high carrier concentration n ⁺ layer 4 and p layer 6 remain.

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 p layer 6 were left. Then, the wafer treated as described above was cut into each element to obtain a pn structure gallium nitride-based light emitting element shown in FIG.

The light emitting device thus obtained had a driving current of 20 mA, an emission peak wavelength of 430 nm, and an emission intensity of 80 to 100 mc.
It was d.

The concentrations of magnesium (Mg) and zinc (Zn) in the light emitting layer 5 are 1 × 10 ¹⁷ to 1 × 10 ²⁰ , respectively.
The range is preferable from the viewpoint of improving the emission intensity.

Second Embodiment FIG. 8 shows the structure of the light emitting diode 10 according to the second embodiment.
In this light emitting diode 10, the light emitting layer 5 is made of magnesium.
It has a multiple thin film structure in which a thin film 51 doped with (Mg) and a thin film 52 doped with zinc (Zn) are repeated. The thickness of the thin films 51 and 52 is 0.05 μm.

The light emitting layer 5 formed on the high carrier concentration n ⁺ 4 is manufactured as follows. Keeping the temperature at 1150 ℃, N ₂ 20 liter / min, NH _{3 10} liter / min, TMG
1.53 × 10 ^-4 mol / min, TMA 0.47 × 10 ^-4 mol / min, TMI
Of 0.02 × 10 ^-4 mol / min and CP ₂ Mg of 2 × 10 ^-7 mol / min
The thin film 51 made of (Al _0.09 Ga _0.91 ) _0.99 In _0.01 N doped with magnesium (Mg) and having a thickness of about 0.05 μm.
Was formed.

Subsequently, the temperature was maintained at 850 ° C. and 20 L of N ₂ was added.
iter / 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 DEZ 3 × Introduce 10 ^-4 mol / min, film thickness approx.
0.05 μm zinc (Zn) doped (Al _0.09 Ga _0.91 ) _0.99
A thin film 52 made of In _0.01 N was formed.

By repeating this, the thin film 51 and the thin film 52
The thin film multi-layers were formed in a total of 6 layers, with 3 as a set.
Then, the p-layer 6 was formed on the uppermost thin film 52 of the multilayer as in the first embodiment. Then, the p layer 6 and the light emitting layer 5
To the layer 5 by irradiating it with an electron beam under the same conditions as in the first embodiment.
Layer 6 was p-conducting. The subsequent manufacturing method is the same as that of the first embodiment.

Third Embodiment FIG. 9 is a diagram showing the structure of a light emitting diode 10 according to the third embodiment. In this light emitting diode 10, the high carrier concentration n ⁺ layer 4 and the light emitting layer 5 are formed of GaN.
The high carrier concentration n ⁺ layer 4 is doped with silicon (Si) and has an electron concentration of 2 × 10 ¹⁸ / cm ³ and a thickness of 2.2 μm.
The light emitting layer 5 has a magnesium (Mg) concentration of 1 × 10 ²⁰ / cm ³ and a zinc (Zn) concentration of 2 × 10 ¹⁸ / cm ³ . The light emitting layer 5 is irradiated with an electron beam under the same conditions as in the first embodiment to be made p-type.

In the first and second embodiments described above, the light emitting layer 5
Is formed in a double heterojunction such that the band gaps of p are smaller than those of the p layer 6 and the high carrier concentration n ⁺ layer 4 existing on both sides. The composition ratios of Al, Ga, In and N 3 in these three layers are selected so as to match the lattice constant of the high carrier concentration n ⁺ layer of GaN.

Although the double heterojunction structure is used in the first and second embodiments, it may be a single heterojunction structure.

Further, in the above-mentioned first and second embodiments,
When the emission peak wavelength is 420 nm, the high carrier concentration n ⁺ layer 4 and the p layer 6 are Al _0.36 Ga _0.56 In _0.08 N, and the emission layer 5 is Al _0.36 Ga _0.56 In _0.08 N. When the emission peak wavelength is 520 nm, the high carrier concentration n ⁺
The layer 4 and the p layer 6 are Al _0.004 Ga _0.091 In _0.905 N, and the light emitting layer 5 is
Al _0.36 Ga _0.56 In _0.08 N

[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.

FIG. 8 is a configuration diagram showing a configuration of a light emitting diode of a second embodiment.

FIG. 9 is a configuration diagram showing a configuration of a light emitting diode of a third 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 6 ... P layer 7, 8 ... Electrode 9 ... Groove

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masayoshi Koike 1 Ochiai, Nagachibata, Kasuga-cho, Nishikasugai-gun, Aichi Prefecture Toyoda Gosei Co., Ltd. (72) Inventor Yu Akasaki 1-38, Jyoshin, Nishi-ku, Aichi Prefecture 805 (72) Inventor Hiroshi Amano Room No. 103, Bldg. 19, Nijigaoka Higashi Danchi, 21-21 Kamioka-cho, Meito-ku, Nagoya, Aichi

Claims (5)

[Claims] 1. A Group III nitride semiconductor (Al _x Ga _Y In _1-XY N; X = 0,
(Including Y = 0, X = Y = 0)), and an n layer showing an n conductivity type,
In a light emitting device having a three-layer structure in which a p-type layer having p-conductivity type and a light-emitting layer interposed between the layers are formed by a mono-junction, a single hetero-junction or a double hetero-junction, the light-emitting layer is ) And zinc (Zn) are added as impurities. 2. A group III nitride semiconductor (Al _x Ga _Y In _1-XY N; X = 0,
(Including Y = 0, X = Y = 0)), and an n layer showing an n conductivity type,
A light emitting device having a p-conduction type light emitting layer, wherein magnesium (Mg) and zinc (Zn) are added as impurities to the light emitting layer. 3. The magnesium (Mg) concentration is 1 × 10 ¹⁸ to
The light emitting device according to claim 1, wherein the light emitting device is added at 1 × 10 ²⁰ / cm ³ . 4. The zinc (Zn) has a concentration of 1 × 10 ¹⁸ to 1 × 10.
The light emitting device according to claim 1 or 2, wherein the light emitting device is added at ²⁰ / cm ³ . 5. The light emitting layer is formed by a thin film multi-layer in which a thin film to which magnesium (Mg) is added and a thin film to which zinc (Zn) is added are repeated. The light emitting device according to claim 1 or 2.