JP3498185B2 - Nitrogen-3 group compound semiconductor light emitting device and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blue-emitting nitrogen-3 group compound semiconductor light emitting device. 2. Description of the Related Art Heretofore, a blue light emitting diode using a GaN-based compound semiconductor has been known. The GaN
Since the compound semiconductor of the system is a direct transition type, it has attracted attention because of its high luminous efficiency and the fact that blue, which is one of the three primary colors of light, is used as the luminescent color. A light emitting diode using such a GaN-based compound semiconductor has a high carrier concentration N made of an N-conductivity type GaN-based compound semiconductor directly on a sapphire substrate or with a buffer layer made of aluminum nitride interposed therebetween. ⁺ 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 ). However, the light emitting intensity of the light emitting diode having the above structure is not yet sufficient, and improvement is desired. Accordingly, an object of the present invention is to provide a compound semiconductor of a nitrogen-3 group element (Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0)
The purpose is to improve the blue light emission intensity of the light emitting diode. [0005] The present invention provides an N-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-type nitrogen-group III element compound semiconductor doped with a P-type impurity (Al _x Ga _Y In _1-XY N; X = 0, Y = 0,
X = Y = 0), and a P-type impurity concentration in the direction away from the junction surface with the N layer. It is characterized in that the structure is increased in multiple stages. The P-type impurity is, for example, Zn. Each I
The growth temperature of the layer is desirably 1000 to 1200 ° C. When crystals were grown in this range, good quality crystals were obtained and emission luminance was improved. When Zn is used as a P-type impurity, I
The impurity concentration of each thin film in 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. 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 a direction away from the bonding surface with the N layer. The efficiency of injection of electrons and holes was improved, and the light emitting portion was made to emit light from the junction surface between the N layer and the I layer and from the I layer. Further, since the impurity atoms at the emission center shift from the high-concentration I layer side to the low-concentration I layer side on the N layer side, the stability of light emission and the prolongation of the element life are achieved. Hereinafter, the present invention will be described with reference to specific examples. First Embodiment 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
^A high carrier concentration N ⁺ layer 3 made of GaN of ¹⁸ / cm ^{3 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, an I layer 5 having a multilayer structure of many thin films is formed on the low carrier concentration N layer 4.
Is formed. The thickness of each thin film of the I layer 5 is 500 °. 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 and 2.0 × 10 ²¹ / cm ³ , and the Zn concentration of the uppermost ultra-high 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 an equi-specific concentration difference of about 5 times. An electrode 8 made of aluminum connected to the ultra-high impurity concentration I _SH layer 6 and the high carrier concentration N ⁺ layer 3
And an electrode 9 formed of aluminum and connected to the electrode 9. Next, a method of manufacturing the light emitting diode 10 having this structure will be described. The light emitting diode 10 includes:
It was manufactured by vapor phase growth using an organometallic compound vapor phase growth method (hereinafter referred to as "M0VPE"). The gas used was NH
₃ and the carrier gas H ₂ and 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 referred to as “DEZ”). First, a single-crystal sapphire substrate 1 whose main surface is the surface A that has been cleaned by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of an MOVPE apparatus. Next, at a temperature of 1100 ° C. while flowing H ₂ at 2 liter / min.
The sapphire substrate 1 was subjected to gas phase etching. [0012] Next, by lowering the temperature to 400 ° C., and H ₂
20 liter / min, NH ₃ 10 liter / min, TMA 1.8 × 10 ^-5
Supplying at mol / min, an AlN buffer layer 2 was formed to a thickness of about 500 °. 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, TMG
Of 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.
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. Subsequently, the temperature of the sapphire substrate 1 is set to 1150 ° C.
, H ₂ at 20 liter / min, NH ₃ at 10 liter / min, TMG
Was supplied at a rate of 1.7 × 10 ⁻⁴ mol / min for 15 minutes, and a film thickness of about 1.
A low carrier concentration N layer 4 of 1 μm and GaN having 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
× 10 ^-4 mol / min, DEZ at an interval of 0.7 minutes, initial value 5
By changing the flow rate in 11 steps from × 10 ⁻¹⁰ mol / min to a ratio of about 5 times, each film thickness is 500 ° and the Zn concentration is 1 × 10 ¹⁵ / cm ³ ~
An I layer 5 having a multi-stage laminated structure varying at a ratio of about 5 in the range of 2.0 × 10 ²¹ / cm ³ was formed. Then, set DEZ to 5 × 10
The gas was supplied for 3 minutes at ^-3 mol / min without changing other gas flow rates to form an ultra-high impurity concentration I _SH layer 6 having a Zn concentration of 1.0 × 10 ²² / cm ³ and a thickness of 0.2 μm. . Thus, a 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 sputtering.
Å was formed. 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 etchant. Next, as shown in FIG. 5, the ultra-high impurity concentration I _SH layer 6 and the 10 I-th layer 60 to the 1 I-th part of the portion 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 ⁺
A part of the upper surface of the layer 3 was vacuumed at 0.04 Torr and high frequency power was 0.44 W /
cm ³ , dry etching of BCl ₃ gas at 10cc / min,
Dry etching with Ar. Next, as shown in FIG. 6, the SiO ₂ layer 11 remaining on the ultra-high impurity concentration I _SH layer 6 was removed with hydrofluoric acid. Next, as shown in FIG. 7, an Al layer 1
3 was formed by vapor deposition. Then, a photoresist 14 is applied on the Al layer 13, and the photoresist 14 is coated with the high carrier concentration N ⁺ layer 3 by photolithography.
A pattern was formed in a predetermined shape so that an electrode portion for the ultra-high impurity concentration I _SH layer 6 remained. Next, as shown in FIG. 7, the exposed portion of the lower Al layer 13 is etched with a nitric acid-based etchant using the photoresist 14 as a mask, the photoresist 14 is removed with acetone, and the high carrier concentration N ⁺ The electrode 9 of the layer 3 and the electrode 8 of the ultra-high impurity concentration I _SH layer 6 were formed. In this way, as shown in FIG.
A gallium nitride-based light emitting device having a (ta-l-Insulator-Semiconductor) structure can be manufactured. When the light emission intensity of the light emitting diode 10 manufactured as described above was measured,
It was 2mcd. This improved light emission intensity by a factor of 10 compared to conventional light emitting diodes. Further, when the light emitting surface was observed, it was also observed that the number of light emitting points increased dramatically. Further, the life of the device has been 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
AlN buffer layer 2 is formed. On the buffer layer 2, a film thickness of about 2.2 μm and a carrier concentration
1.5 × 10 ¹⁸ / cm ³ high carrier concentration N ⁺ layer ³ of GaN, film thickness of about 1.1 μm, carrier concentration of 1 × 10 ¹⁵ / cm ³ Ga
A low carrier concentration N layer 4 of N 2 is formed. Further, on the low carrier concentration N layer 4, an I layer 5 in which the Zn concentration is continuously inclined and increased is formed. Zn of I layer 5
The concentration is changed by a function of a × exp (−αx) + b with respect to an x-axis taken perpendicular to the junction 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 . Α is 3 / μm. An electrode 8 made of aluminum connected to the upper surface of the I layer 5 and an electrode 9 made of aluminum connected to the high carrier concentration N ⁺ layer 3 are formed. The manufacturing method of the light emitting diode 10 having this structure is the same as that of the first embodiment except for the I layer 5. The manufacture of the I layer 5 is performed as follows. 1150 sapphire substrate 1
In the ° C., the H ₂ 20 liter / min, the NH ₃ 10 liter / min,
The TMG was 1.7 × 10 ⁻⁴ mol / min, and the flow rate of DEZ was from the initial value of 5 × 10 ⁻¹⁰ mol / min to 5 × 10 ⁻³ mol / min.
It was changed by a function of c × exp (−βt) + d. Where β =
4.7 / min. In this way, as a result of vapor-phase growth for 7 minutes, the Zn concentration is 1 × 10 ¹⁵ / cm ^{3 on} the NI junction surface, the Zn concentration is 1.0 × 10 ²² / cm ^{3 on} the uppermost surface, and the I layer is 0.5 μm thick. 5 was formed. Next, processing is performed in the same manner as in the first embodiment, and FIG.
The light emitting diode 10 having the structure shown in FIG. The light emission intensity of the light emitting diode 10 manufactured as described above was measured and found to be 2 mcd. This improved light emission intensity by a factor of 10 compared to conventional light emitting diodes. Further, when the light emitting surface was observed, it was also observed that the number of light emitting points increased dramatically. Further, the life of the device has been improved. In the above embodiment, the impurity concentration distribution of Zn in the I layer 5 is a × exp (−αx) + b (α> 0), but a × exp (αx) + b (α > 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 was set to _0.5 In _0.3 N. The high carrier concentration N ⁺ layer 3 was formed to have an electron concentration of 2 × 10 ¹⁸ / cm ³ by adding silicon, and the low carrier concentration N layer 4 was formed to have an electron concentration of 1 × 10 ¹⁶ / cm ³ without adding impurities. . The multiple layers of the I layer 5 are 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 ultra-high impurity concentration I _SH layer 6 in the uppermost layer is 1.0 ×
10 ²² / cm ³ . That is, the Zn concentration of each I layer is formed with an equi-specific concentration difference of about 5 times. And the ultra-high impurity concentration I
An electrode 8 made of aluminum connected to the _SH layer 6 and an electrode 8 made of aluminum 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, and 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 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 manufactured as described above was 2 mcd. This improved light emission intensity by a factor of 10 compared to conventional light emitting diodes. Further, when the light emitting surface was observed, it was also observed that the number of light emitting points increased dramatically. Further, the life of the device has been improved.

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. FIG. 2 is a sectional view showing a manufacturing step of the light-emitting diode of the embodiment. FIG. 3 is a sectional view showing a step of manufacturing the light-emitting diode of the example. FIG. 4 is a sectional view showing the manufacturing process of the light-emitting diode of the embodiment. FIG. 5 is a sectional view showing the manufacturing process of the light emitting diode of the same embodiment. FIG. 6 is a sectional view showing the manufacturing process of the light-emitting diode of the example. FIG. 7 is a sectional view showing the manufacturing process of the light emitting diode of the same embodiment. FIG. 8 is a configuration diagram showing a configuration of a light emitting diode of a second embodiment. DESCRIPTION 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 ... First I layer 60 ... 10 I layer 6 ... Ultra high Impurity concentration I _SH layer 7 ... electrode 8 ... electrode

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Umezaki 1 Ochiai Ochiai, Kasuga-cho, Nishikasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. (56) References JP-A-4-199752 (JP, A) JP-A Heisei 4-163971 (JP, A) JP-A-4-163970 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 33/00

Claims (1)

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