JPH06151967A - Nitrogen-iii compound semiconductor luminous element and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the luminance and life of an AlGaInN light emitting diode. CONSTITUTION:The title luminous element consists of an n-layer made of n-type gallium nitride (GaN) and i-layer made of i-type gallium nitride with p-type impurities added. The i-layer 5 consists of a large number of laminated thin films wherein the p-type impurity concentration is stepwise increased in the direction away from the junction with the n-layer 4. The i-layer 5 may be so structured that the p-type impurity concentration is gradually increased therein. The Zn concentration is varied within the range of 1X10<15>/cm<3>-2.0X10<21>/cm<3>. The structure mentioned above improves the electron injection efficiency, luminance and element life.

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 nitrogen-group III compound semiconductor light-emitting device.

[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
Since the compound semiconductors of the type are direct transition type, they have high luminous efficiency, and blue, which is one of the three primary colors of light, is used as the emission color, and so on.

A light emitting diode using such a GaN-based compound semiconductor has a high carrier concentration N formed of an N-conductivity type GaN-based compound semiconductor directly or on a sapphire substrate with a buffer layer made of aluminum nitride interposed. ⁺ layer and the low carrier concentration N layer, that has a structure which is grown a lightly doped I _L layer and the high impurity concentration I _H layer on the low carrier concentration N layer (JP-a-3-252177 JP ).

[0004]

However, the light emission intensity of the light emitting diode having the above structure is not yet sufficient, and improvement is desired. Therefore, an object of the present invention is to provide a nitrogen-3 group compound semiconductor (including Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0).
It is to improve the blue emission intensity of the light emitting diode.

[0005]

The present invention is directed to N-type nitrogen-
Group 3 element compound semiconductor (Al _x Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0
And a P-type impurity-added I-type nitrogen-group 3 element compound semiconductor (Al _x Ga _Y In _1-XY N; X = 0, Y = 0,
X = Y = 0) and an I layer made of (3), and the P type impurity concentration is continuously or in the direction of moving the I layer away from the joint surface with the N layer. The feature is that the structure is increased in multiple stages.

The P-type impurity is Zn, for example. Each I
The layer growth temperature is preferably 1000 to 1200 ° C. When crystals were grown in this range, good quality crystals were obtained and the emission brightness was improved.

When Zn is used as the P-type impurity, I
The impurity concentration of each thin film of the layer is 1 × 10 ¹⁵ to 1 × 10 ²² / cm ³
It is desirable to increase continuously or in multiple steps within the range.

[0008]

According to the present invention, the I layer has a structure in which the P-type impurity concentration is increased continuously or in multiple steps in the direction away from the junction surface with the N layer. The injection efficiency of the holes was improved, and the emission brightness was improved because the light emitting portion started to emit light from the bonding surface between the N layer and the I layer and the I layer. Further, since the impurity atom at the luminescence center migrates from the high-concentration I layer side to the N-layer side low-concentration I layer side, the stability of light emission and the prolongation of the device life are achieved.

[0009]

EXAMPLES The present invention will be described below based on specific examples. First Embodiment In FIG. 1, a light emitting diode 10 has a sapphire substrate 1, and the sapphire substrate 1 has 500 Å AlN.
Buffer layer 2 is formed. On the buffer layer 2, a film thickness of about 2.2 μm and a carrier concentration of 1.5 × 10
^A high carrier concentration N ⁺ layer 3 made of ¹⁸ / cm ³ GaN and a low carrier concentration N layer 4 made of GaN having a film thickness of about 1.1 μm and a carrier concentration of 1 × 10 ¹⁵ / cm ³ are formed. Further, on the low carrier concentration N layer 4, an I layer 5 having a multi-layered thin film structure is formed.
Are formed. The thickness of each thin film of the I layer 5 is 500Å. The Zn concentration of each of the thin films 51 to 60 of the I layer 5 is 1 ×
10 ¹⁵ / cm ³ , 5.0 × 10 ¹⁵ / cm ³ , 2.5 × 10 ¹⁶ / cm ³ , 1.
3 × 10 ¹⁷ / cm ³ , 6.3 × 10 ¹⁷ / cm ³ , 3.2 × 10 ¹⁸ / c
m ³ , 1.6 × 10 ¹⁹ / cm ³ , 7.9 × 10 ¹⁹ / cm ³ , 4.0 × 10
²⁰ / cm ³ , 2.0 × 10 ²¹ / cm ³ , and the Zn concentration of the uppermost ultrahigh impurity concentration I _SH layer 6 is 1.0 × 10 ²² / cm ³ . That is, the Zn concentration of each I layer is formed with a difference of about 5 times in equi-concentration. Then, the electrode 8 formed of aluminum and the high carrier concentration N ⁺ layer 3 connected to the ultra-high impurity concentration I _SH layer 6 are formed.
And an electrode 9 made of aluminum that is connected to.

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 gas used is NH
₃ and carrier gas H ₂ and trimethylgallium (Ga (CH ₃ ) ₃ ).
(Hereinafter referred to as "TMG") and trimethyl aluminum (Al
(CH _{3) 3)} (a hereinafter referred to as "TMA") and silane (SiH ₄₎ and diethyl zinc (hereinafter referred to as "DEZ").

First, the single-crystal sapphire substrate 1 whose main surface is the A-plane, which has been cleaned by organic cleaning and heat treatment, is mounted on the susceptor mounted in the reaction chamber of the M0VPE apparatus. Then, at a normal pressure of H ₂ at a rate of 2 liters / minute, the temperature was 1100 ° C. while flowing into the reaction chamber.
Then, the sapphire substrate 1 was vapor-phase etched.

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 maintained at 1150 ° C., H ₂ is 20 liter / min, NH ₃ is 10 liter / min, and TMG is
Silane (SiH ₄ ) diluted to 1.7 × 10 ^-4 mol / min and 0.86 ppm with H ² at a rate of 200 ml / min for 30 minutes to obtain a film thickness of approximately
2.2 .mu.m, to form a high carrier concentration N ⁺ layer 3 made of GaN having a carrier concentration 1.5 × 10 ¹⁸ / cm ^3.

Then, the temperature of the sapphire substrate 1 is set to 1150 ° C.
, H ₂ 20 liter / min, NH ₃ 10 liter / min, TMG
Is supplied at a rate of 1.7 × 10 ^-4 mol / min for 15 minutes to obtain a film thickness of about 1.
A low carrier concentration N layer 4 made of GaN having a carrier concentration of 1 μm and a carrier concentration of 1 × 10 ¹⁵ / cm ³ was formed.

Next, the sapphire substrate 1 is heated to 1150 ° C.,
H ₂ 20 liter / min, NH ₃ 10 liter / min, TMG 1.7
Initial value 5 × 10 ^-4 mol / min, DEZ at intervals of 0.7 min
The flow rate was changed from 11 × 10 ^-10 mol / min to about 5 times in 11 steps to obtain a film thickness of 500 Å and a Zn concentration of 1 × 10 ¹⁵ / cm ³ 〜
An I layer 5 having a multi-step laminated structure was formed in which the ratio was changed by about 5 times in the range of 2.0 × 10 ²¹ / cm ³ . Next, set DEZ to 5 × 10.
^-3 mol / min, the other gas flow rate was not changed and was supplied for 3 minutes to form an ultrahigh impurity concentration I _SH layer 6 having a Zn concentration of 1.0 × 10 ²² / cm ³ and a thickness of 0.2 μm. . In this way, the wafer having the structure shown in FIG. 2 was obtained.

Next, as shown in FIG. 3, an SiO ₂ layer 11 is formed on the ultra-high impurity concentration I layer 6 by a sputtering method.
Formed to a thickness of Å. Next, a photoresist 12 was applied on the SiO ₂ layer 11, and the photoresist 12 was formed by photolithography in a pattern in which the photoresist at the electrode formation site for the high carrier concentration N ⁺ layer 3 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-based etching solution. Next, as shown in FIG. 5, the ultrahigh impurity concentration I _SH layer 6 and the 10th I layer 60 to the 1Ith region not covered by the photoresist 12 and the SiO ₂ layer 11 are formed.
Layer 51, low carrier concentration N layer 4 and high carrier concentration N ⁺
Part of the upper surface of layer 3 has a vacuum degree of 0.04 Torr and high frequency power of 0.44 W /
After the cm ^3, BCl ₃ gas was dry-etched with 10 cc / min,
It was dry-etched with Ar.

Next, as shown in FIG. 6, the SiO ₂ layer 11 remaining on the ultrahigh impurity concentration I _SH layer 6 was removed with hydrofluoric acid. Next, as shown in FIG. 7, an Al layer 1 is formed on the entire upper surface of the sample.
3 was formed by vapor deposition. Then, a photoresist 14 is applied on the Al layer 13, and the photoresist 14 is formed into a high carrier concentration N ⁺ layer 3 by photolithography.
And a pattern was formed in a predetermined shape so that the electrode portion for the ultrahigh impurity concentration I _SH layer 6 remained.

Next, as shown in FIG. 7, the exposed portion of the underlying Al layer 13 is etched with a nitric acid-based etching solution using the photoresist 14 as a mask, and the photoresist 14 is removed with acetone to obtain a high carrier concentration N ^+. The electrode 9 of the layer 3 and the electrode 8 of the ultrahigh impurity concentration I _SH layer 6 were formed.

In this way, as shown in FIG. 1, MIS (Me
It is possible to manufacture a gallium nitride-based luminescent element having a ta-l-Insulator-Semiconductor) structure. When the emission intensity of the light emitting diode 10 manufactured in this way was measured,
It was 2 mcd. This is a 10-fold improvement in light emission intensity compared to conventional light emitting diodes. Moreover, when the light emitting surface was observed, it was also observed that the number of light emitting points increased dramatically. Further, the device life is also improved.

Second Embodiment Next, a light emitting diode according to a second embodiment will be described. In FIG. 8, the light emitting diode 10 has a sapphire substrate 1, and the sapphire substrate 1 has 500 Å
AlN buffer layer 2 is formed. On the buffer layer 2, a film thickness of about 2.2 μm and a carrier concentration
High carrier concentration N ⁺ layer 3 consisting of 1.5 × 10 ¹⁸ / cm ³ GaN, film thickness about 1.1 μm, carrier concentration 1 × 10 ¹⁵ / cm ³ Ga
A low carrier concentration N layer 4 made of N 2 is formed. Further, the I layer 5 in which the Zn concentration is continuously inclined and increased is formed on the low carrier concentration N layer 4. Zn of I layer 5
The concentration is changed by a function of a × exp (−αx) + b with respect to the x axis taken perpendicularly to the joining surface between the I layer 5 and the N layer 4. However, the Zn concentration at the position of x = 0 is 1 × 10 ¹⁵
/ cm ³ , and the Zn concentration at the position of x = 0.7 μm on the uppermost surface is 1.0 × 10 ²² / cm ³ . Further, α is 3 / μm. Then, an electrode 8 formed of aluminum and connected to the upper surface of the I layer 5 and an electrode 9 formed of aluminum and connected to the high carrier concentration N ⁺ layer 3 are formed.

The method of manufacturing the light emitting diode 10 having this structure is the same as that of the first embodiment except the I layer 5. The I layer 5 is manufactured as follows. Sapphire substrate 1 1150
In the ° C., the H ₂ 20 liter / min, the NH ₃ 10 liter / min,
TMG 1.7 x 10 ^-4 mol / min, DEZ flow rate from the initial value 5 x 10 ^-10 mol / min to 5 x 10 ^-3 mol / min,
It was changed by a function of c × exp (−βt) + d. However, β =
4.7 / min. In this way, as a result of vapor phase growth for 7 minutes, the Zn concentration at the NI junction surface was 1 × 10 ¹⁵ / cm ³ , the Zn concentration at the uppermost surface was 1.0 × 10 ²² / cm ³ , and the thickness of the I layer was 0.5 μm. 5 was formed.

Next, the same process as in the first embodiment is performed, and the process shown in FIG.
A light emitting diode 10 having the structure shown in was formed. The light emission intensity of the light emitting diode 10 thus manufactured was measured and found to be 2 mcd. This is a 10-fold improvement in light emission intensity compared to conventional light emitting diodes. Moreover, when the light emitting surface was observed, it was also observed that the number of light emitting points increased dramatically. Further, the device life is also improved.

In the above embodiment, the Zn impurity concentration distribution of the I layer 5 is axexp (-αx) + b (where α> 0), but a × exp (αx) + b (where α is It may be increased by a function of> 0). Further, it may be changed by another function.

Third Embodiment In the light emitting diode of the first embodiment having the structure shown in FIG. 1, a high carrier concentration N ⁺ layer 3, a low carrier concentration N layer 4,
The I layer 5 and the ultra-high impurity concentration I _SH layer 6 are each made of Al _0.2 G
a _0.5 In _0.3 N. The high carrier concentration N ⁺ layer 3 was formed by adding silicon to an electron concentration of 2 × 10 ¹⁸ / cm ³ , and the low carrier concentration N layer 4 was formed without adding impurities to an electron concentration of 1 × 10 ¹⁶ / cm ³ . . The multi-layer of the I layer 5 is made of Zn as in the first embodiment.
The concentrations are 1 × 10 ¹⁵ / cm ³ and 5.0 × 10 ¹⁵ / c, respectively.
m ³ , 2.5 × 10 ¹⁶ / cm ³ , 1.3 × 10 ¹⁷ / cm ³ , 6.3 × 10 ¹⁷
/ cm ³ , 3.2 × 10 ¹⁸ / cm ³ , 1.6 × 10 ¹⁹ / cm ³ , 7.9 ×
10 ¹⁹ / cm ³ , 4.0 × 10 ²⁰ / cm ³ , 2.0 × 10 ²¹ / cm ^3, and the Zn concentration of the uppermost ultrahigh impurity concentration I _SH layer 6 is 1.0 ×
It was set to 10 ²² / cm ³ . That is, the Zn concentration of each I layer is formed with a difference of about 5 times in equi-concentration. And the ultra-high impurity concentration I
An electrode 8 made of aluminum and connected to the _SH layer 6 and an electrode 8 made of aluminum and connected to the high carrier concentration N ⁺ layer 3 are formed.

Next, the light emitting diode 10 having this structure can be manufactured similarly to the light emitting diode of the first embodiment. Trimethylindium (In (CH ₃ ) ₃ ) was used in addition to TMG, TMA, silane, CP ₂ Mg gas. The generation temperature and gas flow rate are the same as in the first embodiment. The flow rates of the other gases are the same as those in the first embodiment except that trimethylindium is supplied at 1.7 × 10 ⁻⁴ mol / min.

The light emission intensity of the light emitting diode 10 thus manufactured was measured and found to be 2 mcd. This is a 10-fold improvement in light emission intensity compared to conventional light emitting diodes. Moreover, when the light emitting surface was observed, it was also observed that the number of light emitting points increased dramatically. Further, the device life is also improved.

[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 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.

[Explanation of symbols]

10 ... Light emitting diode 1 ... Sapphire substrate 2 ... Buffer layer 3 ... High carrier concentration N ⁺ layer 4 ... Low carrier concentration N layer 5 ... I layer 51 ... 1st I layer 60 ... 10I layer 6 ... Ultra high impurity concentration I _SH layer 7 ... Electrode 8 ... Electrode

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masato Tamaki 1 Ochiai, Nagachi, Kasuga-cho, Nishikasugai-gun, Aichi Toyoda Gosei Co., Ltd. Toyoda Gosei Co., Ltd.

Claims (1)

[Claims] 1. An N-type nitrogen-3 group element compound semiconductor (Al _x
Ga _Y In _1-XY N; X = 0, Y = 0, X = Y = 0)
I consisting of I-type nitrogen-group 3 element compound semiconductor (Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0) doped with P-type impurities
A nitrogen-3 group element compound semiconductor light emitting device having a layer, the I layer in a direction away from a bonding surface with the N layer,
A light emitting device having a structure in which the P-type impurity concentration is increased continuously or in multiple steps.