JP3193981B2 - Gallium nitride based compound semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a nitrogen-gallium-based compound semiconductor light-emitting device that emits blue light.

[Prior art]

Conventionally, a blue light emitting diode using a GaN-based compound semiconductor has been known. Since the GaN-based compound semiconductor is a direct transition, the luminous efficiency is high,
Attention has been paid to making blue, one of the three primary colors of light, the emission color. A light emitting diode using such a GaN-based compound semiconductor grows an N-layer made of an N-type conductive GaN-based compound semiconductor on a sapphire substrate directly or with a buffer layer made of aluminum nitride interposed therebetween. A structure in which a P-type impurity is added to the N-layer to grow an I-layer made of an I-type GaN-based compound semiconductor (Japanese Patent Laid-Open No. Sho 62-62).
119196, JP-A-63-188977).

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 improve the blue light emission intensity of a GaN-based compound semiconductor light emitting diode.

[Means for Solving the Problems]

The present invention provides an N-type gallium-based compound semiconductor (Al _X G
a _1-X N; including X = 0) and an I-type nitrogen-gallium-based compound semiconductor (Al _X Ga _1-X N;
X = 0 (including X = 0) in the nitrogen-gallium-based compound semiconductor light-emitting device having an I layer.
Layer and a high carrier concentration N ⁺ layer.
It has a double-layer structure consisting of a low-impurity-concentration _IL layer with a relatively low concentration of P-type impurities and a high-impurity-concentration _IH layer with a relatively high concentration of P-type impurities, in order from the side that joins the layers And The carrier concentration of the low carrier concentration N layer is 1 × 10
^The thickness is preferably ¹⁴ to 1 × 10 ¹⁷ / cm ³ and the thickness is 0.5 to 2 μm. When the carrier concentration is 1 × 10 ¹⁷ / cm ³ or more, the emission intensity is decreased. Undesirably, when the carrier concentration is 1 × 10 ¹⁴ / cm ³ or less, the series resistance of the light-emitting element becomes too high and heat is generated when a current is applied. . On the other hand, when the film thickness is 2 μm or more, the series resistance of the light emitting element becomes excessively high, and heat is generated when an electric current is applied. Further, the carrier concentration of the high carrier concentration N ⁺ layer is 1 × 10 ¹⁷
It is preferable that the thickness is 1 to 10 μm at 1 × 10 ¹⁹ / cm ³ . If the carrier concentration is 1 × 10 ¹⁹ / cm ³ or more, the crystallinity is deteriorated, and if it is 1 × 10 ¹⁷ / cm ³ or less, the resistance becomes high, which is not desirable. On the other hand, when the film thickness is 10 μm or more, the substrate is undesirably curved, and when the film thickness is 1 μm or less, high resistance is undesirably obtained. The P-type impurity concentration of the low impurity concentration _IL layer is 1 × 10
^The thickness is preferably ^{16 to} 5 × 10 ¹⁹ / cm ³ and the thickness is preferably 0.01 to 1 μm. P
Since type impurity concentration is rising voltage or series resistance increases the light emitting diode becomes 5 × 10 ¹⁹ / cm ³ or more is increased undesirably, undesirable since 1 × 10 ¹⁶ / cm ³ or less when it comes to the N conductivity type . On the other hand, if the film thickness is 1 μm or more, the series resistance of the light-emitting diode increases and the rise voltage rises, which is not desirable. Further, the film thickness impurity concentration at ^{1 × 10 19 ~5 × 10 20} / cm 3 of high impurity concentration I _H layer 0.02~0.3μm is desirable. The impurity concentration is 5 × 10 ²⁰ /
If it is more than cm ³ , crystallinity deteriorates, which is not desirable,
When the density is less than 1 × 10 ¹⁹ / cm ³ , the emission intensity is undesirably reduced. On the other hand, when the film thickness is 0.3 μm or more, the resistance becomes high, which is not desirable. When the film thickness is 0.02 μm or less, the I layer is destroyed, which is not desirable.

Function and Effect of the Invention

The present invention provides a double layer structure of a low carrier concentration N layer and a high carrier concentration N ⁺ layer in order from the side where the N layer is joined to the I layer, and a P-type impurity in order from the side where the I layer is joined to the N layer. Has a double-layered structure of a relatively low-concentration low-impurity-concentration _IL layer and a relatively high-concentration high-impurity-concentration _IH layer having a relatively high concentration of P-type impurities.
The blue light emission intensity of the light emitting diode could be increased. That is, the electric resistance of the entire N layer can be reduced by the high carrier concentration N ⁺ layer, and a voltage can be effectively applied to the junction between the I layer and the low carrier concentration N layer. Further, by making the N layer bonded to the I layer have a low carrier concentration, diffusion or mixing of non-emitting impurity atoms of the N layer into the I layer can be prevented.
Further, when electrons are injected from the N layer to the I layer, the I layer joined to the N layer is formed as the low impurity concentration _IL layer, so that the electrons are not trapped in the low impurity concentration _IL layer. It is implanted into the next high impurity concentration I _H layer. For this reason, the electrons pass through the low impurity concentration I _L layer joined to the N layer having poor luminous efficiency, reach the high impurity concentration I _H layer, and emit light with high efficiency in that layer. As a result, the luminous efficiency was dramatically improved as compared with the conventional simple IN junction.

【Example】

Hereinafter, the present invention will be described based on specific examples. In FIG. 1, a light emitting diode 10 has a sapphire substrate 1, and the sapphire substrate 1
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 ¹⁸
/ cm ³ GaN high carrier concentration N ⁺ layer 3, about 1.5μ thick
m, a low carrier concentration N layer 4 made of GaN having a carrier concentration of 1 × 10 ¹⁵ / cm ³ , a low impurity concentration _IL layer 5 having a Zn concentration of 5 × 10 ¹⁹ / cm ³ and a Zn concentration of 2 × 10 ²⁰ / cm ³ . A high impurity concentration _IH layer 6 is formed. Then, an electrode 7 made of aluminum connected to the high impurity concentration I _H layer 6 and an electrode 8 made of aluminum connected to the high carrier concentration N ⁺ layer 3 are formed. Next, a method for manufacturing the light emitting diode 10 having this structure will be described. The light emitting diode 10 was manufactured by vapor phase growth using a metal organic compound vapor phase epitaxy method (hereinafter referred to as “MOVPE”). The gases used were NH ₃ , carrier gas H ₂ , trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”), and trimethylaluminum (Al (CH ₃ ) ₃ ) (hereinafter referred to as “TMA”). ), Silane (SiH ₄ ) and diethylzinc (hereinafter “DEZ”)
Is written). First, a single-crystal sapphire substrate 1 whose main surface is a c-plane cleaned by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of a MOVPE apparatus. Next, while flowing H ₂ at a normal pressure into the reaction chamber at a rate of 2 / minute,
The sapphire substrate 1 was subjected to gas phase etching at 1100 ° C. Then, by lowering the temperature to 400 ° C., the H ₂ 20 / min, N
H ₃ 10 / min, AlN supplied at 1.8 × 10 ^-5 mol / min TMA
Was formed to a thickness of about 500 °. Then, maintaining the temperature of the sapphire substrate 1 to 1150 ° C., H ₂
20 / min, NH ₃ 10 / min, TMG 1.7 × 10 ⁻⁴ mol /
Silane (SiH ₄ ) diluted to 0.86 ppm with H ₂
And a carrier concentration of 1.5 × 10 ¹⁸ / cm ³ , to form a high carrier concentration N ⁺ layer 3 of GaN having a thickness of about 2.2 μm and a carrier concentration of 1.5 × 10 ¹⁸ / cm ³ . Subsequently, the temperature of the sapphire substrate 1 is maintained at 1150 ° C.
H ₂ at 20 / min, NH ₃ at 10 / min, TMG at 1.7 × 10 ⁻⁴ mol /
And a low carrier concentration N layer 4 made of GaN having a film thickness of about 1.5 μm and a carrier concentration of 1 × 10 ¹⁵ / cm ^3.
Was formed. Then the sapphire substrate 1 to 1000 ° C., H ₂ 20 /
Min, the NH ₃ 10 / min, 1.7 × 10 ^-4 mol / min TMG, the DEZ 1.
It is supplied at a rate of 5 × 10 ^-4 mol / min for 2 minutes to give a film thickness of 0.2 μm.
Low impurity concentration I _{L with} Zn concentration of 5 × 10 ¹⁹ / cm ³ consisting of m and GaN
Layer 5 was formed. Subsequently, the sapphire substrate 1 was set to 900, and H ₂ was changed to 20 /
Min, the NH ₃ 10 / min, 1.7 × 10 ^-4 mol / min TMG, the DEZ 1.
It is supplied at a rate of 5 × 10 ^-4 mol / min for 2 minutes to give a film thickness of 0.2 μm.
High impurity concentration I _{H with} Zn concentration of 2 × 10 ²⁰ / cm ³ consisting of m and GaN
Layer 6 was formed. Thus, a multilayer structure as shown in FIG. 2 was obtained. Next, as shown in FIG. 3, an SiO ₂ layer 11 was formed on the high impurity concentration I _H layer 6 to a thickness of 2000 ° by sputtering. Next, a photoresist 12 is applied on the SiO ₂ layer 11, and the photoresist is applied by photolithography.
12 was formed 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 etchant. Next, as shown in FIG.
A portion of the upper surface of the high impurity concentration I _H layer 6 at a portion not covered by the O ₂ layer 11, the low impurity concentration _IL layer 5, the low carrier concentration N layer 4, and the high carrier concentration N ⁺ layer 3 Vacuum 44Tor
r, dry etching was performed with a high frequency power of 0.44 W / cm ³ and CCl ₂ F ₂ gas at a rate of 10 cc / min, followed by dry etching with Ar. Next, as shown in FIG. 6, Si remaining on I _H layer 6
The O ₂ layer 11 was removed with hydrofluoric acid. Next, as shown in FIG. 7, an Al layer 13
Was formed by vapor deposition. Then, a photoresist 14 is applied on the Al layer 13 and a predetermined photolithography is performed so that the photoresist 14 has an electrode portion for the high carrier concentration N ⁺ layer 3 and the high impurity concentration I _H layer 6. A pattern was formed into a shape. Next, as shown in FIG. 7, using the photoresist 14 as a mask, the exposed portion of the lower Al layer 13 is etched with a nitric acid-based etchant, the photoresist 14 is removed with acetone, and the high carrier concentration N ⁺ layer 3 is removed. And the electrode 7 of the high impurity concentration _IH layer 6 were formed. In this manner, as shown in FIG. 1, the MIS (Metal-In
A gallium-based luminous element having a (sulator-semiconductor) structure can be manufactured. The light emission intensity of the light-emitting diode 10 manufactured as described above was 0.2 mcd. This is compared with a conventional light emitting diode in which an I layer having a carrier concentration of 2 × 10 ²⁰ / cm ³ and a thickness of 0.2 μm is simply connected to an N layer having a carrier concentration of 5 × 10 ¹⁷ / cm ³ and a thickness of 4 μm. The luminous intensity was improved eight times. Further, when the light emitting surface was observed, it was also observed that the number of light emitting points increased dramatically. In addition, the above-mentioned sample in which the carrier concentration of the low carrier concentration N layer 4 was variously changed was manufactured, and the light emission intensity and the light emission spectrum were measured. The results are shown in FIG. It can be seen that the emission intensity decreases and the emission wavelength shifts to the red side as the carrier concentration increases. In addition, samples having the above-described structure in which the impurity concentration of the high impurity concentration _IH layer 6 was varied in various ways were manufactured, and the relationship between the impurity concentration, the light emission intensity, and the light emission spectrum was measured. The result is
As shown in FIG. The emission intensity increases as the impurity concentration increases. However, the emission wavelength slightly shifted to the red side, but about 48
It turns out that it stabilizes at 50Å.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a specific embodiment of the present invention, FIGS. 2 to 7 are cross-sectional views showing manufacturing steps of the light emitting diode of the embodiment, FIG. FIG measurement diagram showing the relationship between the carrier concentration of the low carrier concentration N layer and the emission intensity and emission wavelength, FIG. 9 is a high impurity concentration I _H
FIG. 4 is a measurement diagram showing a relationship between an impurity concentration of a layer, an emission intensity, and an emission wavelength. 10 light emitting diode, 1 sapphire substrate 2 buffer layer 3 high carrier concentration N ⁺ layer 4 low carrier concentration N layer 5 low impurity concentration I _L layer 6 high impurity concentration I _H layer, 7,8 …… Electrode

──────────────────────────────────────────────────続 き Continuing on the front page (73) Patent holder 999999999 Japan Science and Technology Corporation 4-1-8, Honcho, Kawaguchi-shi, Saitama (72) Inventor Katsuhide Mabe 1 Ochiai-Ochiagai, Nagasahata Within Toyoda Gosei Co., Ltd. Inside (72) Inventor Norikatsu Koide 1 Ochiai Nagahata, Kasuga-mura, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. Inside Toyota Central Research Laboratory Co., Ltd. (72) Inventor Isamu Isamachi, Chikusa-ku, Nagoya, Aichi On-campus (56) References JP-A-53-34486 (JP, A) JP-A-59-228776 (JP, A) JP-A-63-188977 (JP, A) JP-A-62-119196 (JP, A) Actual Opening Sho 64-17484 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 33/00 H01L 21/205

Claims (1)

(57) [Claims] 1. An N-type nitrogen gallium-based compound semiconductor (Al _X G
a _1-X N; including X = 0) and an I-type nitrogen-gallium-based compound semiconductor (Al _X Ga _1-X N;
X = 0 (including X = 0), and a nitrogen-gallium-based compound semiconductor light-emitting device having an I layer composed of a low carrier concentration N layer and a high carrier concentration N ⁺ layer in order from the side where the N layer is joined to the I layer. A double-layer structure, in which, from the side where the I layer is joined to the N layer, the P-type impurity has a relatively low concentration of a low impurity concentration I _L layer and the P-type impurity has a relatively high concentration of a high impurity concentration I L A light-emitting element having a double-layer structure with an _H layer.