JPH079999B2 - Gallium nitride compound semiconductor light emitting device - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to the structure of a gallium nitride-based compound semiconductor light emitting device.

[Prior art]

Conventionally, a gallium nitride-based compound semiconductor (Al _x Ga _1-x ) has been used by using a metal organic chemical vapor deposition method (hereinafter referred to as “MOVPE”).
A light emitting device having a structure in which a thin film (including N; X = 0) is vapor-phase grown on a sapphire substrate has been studied. As shown in FIG. 5, this light emitting device has a sapphire substrate 1
An N layer 2 made of N-type GaN and an I layer 3 made of I-type GaN formed by doping with zinc are formed thereon, and an electrode 5 and an N layer 2 are formed on the upper surface of the I layer 3. The electrode 6 is formed on the side surface of the.

[Problems to be Solved by the Invention]

As described above, since the light emitting element uses the sapphire substrate, the position of the electrode 6 is on the side surface of the N layer 2 and there is a problem that the manufacturing is difficult. When the electrode of the N layer 2 is formed on the same surface as the electrode 5 of the I layer 3, the insulating film deposited in a predetermined pattern is used as a mask to selectively form the I layer, and then the insulating film is formed. Attempts have been made to form electrodes on the exposed and exposed N layer. However, there is a problem that it is difficult to selectively grow the I layer using the insulating film as a mask, and it is difficult to remove only the insulating film because the I layer is formed on the insulating film. The present invention has been made to solve the above problems, and an object thereof is to facilitate the production of a gallium nitride-based compound semiconductor light emitting device.

[Means for solving problems]

The configuration of the invention for solving the above problems is a sapphire substrate, a buffer layer formed on the sapphire substrate,
An N layer made of an N-type gallium nitride-based compound semiconductor (including Al _x Ga _1-x N; X = 0) formed on the buffer layer;
A silicon dioxide (SiO ₂ ) thin film patterned so that an electric current can pass through the main surface of the layer, and a silicon dioxide thin film is selectively grown by doping impurities on the patterned N layer. An I layer made of an I-type gallium nitride-based compound semiconductor (including Al _x Ga _1-x N; X = 0) joined to the layer, and formed on the silicon dioxide thin film simultaneously with the growth of the I layer. That is, a non-single-crystal conductive layer bonded to the silicon thin film and an electrode layer bonded to the surface of the I layer and the conductive layer are provided.

[Action]

A buffer layer is formed on a sapphire substrate, and an N layer of GaN is formed on the buffer layer. Then, when the I-type gallium nitride compound semiconductor is vapor-deposited using the silicon dioxide thin film patterned as thin as an electric current can pass through the main surface of the N layer, it is masked by the silicon dioxide thin film. A single crystal I-type gallium nitride-based compound semiconductor grows in the non-existing portion, that is, in the portion where the N layer is exposed, but it was tested that the single crystal does not grow on the silicon dioxide thin film and becomes polycrystalline or amorphous. Found out. Since the non-single-crystal gallium nitride compound semiconductor layer (conductive layer) grown on this silicon dioxide thin film is more conductive than the single-crystal I layer, the silicon dioxide thin film is thin enough to have conductivity. Once formed,
The conductive layer can be a lead for the N layer. Therefore, by utilizing the selective growth property of the gallium nitride-based compound semiconductor for the silicon dioxide thin film as described above, the electrode of the I layer and the electrode of the N layer can be easily formed on the same surface. The current from the N layer passes through the silicon dioxide film and reaches the conductive layer.

【Example】

Hereinafter, the present invention will be described based on specific examples. FIG. 1 is a sectional view showing the structure of a vapor phase growth apparatus according to a specific embodiment of the present invention. In the reaction chamber 20 surrounded by the quartz reaction tube 21, the susceptor 22 is supported by the operation rod 23,
The position of the susceptor 22 is adjusted by the operation rod 23. A sapphire substrate 24 is arranged on the main surface of the susceptor 22. In addition, 8 is a high frequency coil for heating the sapphire substrate 24. On the other hand, on the gas inflow side of the reaction chamber 20, the first reaction gas pipe 25
And a second reaction gas pipe 26. The first reaction gas pipe 25 is concentric with the second reaction gas pipe 26,
Is installed inside the. The first reaction gas pipe 25 is the first
The second reaction gas pipe 26 is connected to the manifold 27, and the second reaction gas pipe 26 is connected to the second manifold 28. The first manifold 27 has an NH ₃ supply system H, a carrier gas supply system I, a trimethylgallium (hereinafter “TNG”) supply system J, and a trimethylaluminum (hereinafter “TMA”) supply system. K is connected to the second manifold 28, and a carrier gas supply system I and diethyl zinc (hereinafter referred to as “DE
Z)) supply system L is connected. With such a device configuration, the opening of the first reaction gas pipe 25
From 25a, a mixed gas of NH ₃ , TMG, TMA and H ₂ flows into the reaction chamber 20, and from the opening 26a of the second reaction gas pipe 26, a mixed gas of DEZ and H ₂ flows into the reaction chamber 20. To do. When forming an N-type Al _x Ga _1-x N thin film, it is sufficient to let the mixed gas flow out only from the first reaction gas pipe 25.
_When forming the _x Ga _{1 -x} N thin film, the mixed gas of each of the first reaction gas pipe 25 and the second reaction gas pipe 26 may be discharged. When forming an I-type Al _x Ga _1-x N thin film,
The dopant gas DEZ is mixed with the reaction gas flowing out from the first reaction gas pipe 25 in the reaction chamber 20a near the sapphire substrate 24 for the first time. Then, DEZ is sprayed onto the sapphire substrate 24 and thermally decomposed, and the dopant element is doped into the growing Al _x Ga _1-x N to form I-type Al _x Ga _1-x N.
Is obtained. In this case, the first reaction gas pipe 25 and the second reaction gas pipe 26 are separated, and the reaction gas and the dopant gas are introduced to the reaction chamber 25a near the sapphire substrate 24. DEZ and TMG or TMA in
Since the reaction with is suppressed, good doping is performed. The inclination angle θ of the susceptor 22 with respect to the reaction gas flow direction X is set to 45 degrees. By inclining in this way, good crystals were obtained as compared with the case where the susceptor 22 was configured at right angles to the gas flow. Next, a method for producing a light emitting diode having the structure shown in FIG. 2 by using this device will be described. First, a single crystal sapphire substrate 24 whose main surface is the (0001) plane cleaned by organic cleaning and heat treatment is mounted on the susceptor 22. Next, at a temperature of 1100 ° C. while flowing H ₂ at 0.3 l / min into the reaction chamber 20 from the first reaction gas pipe 25 and the second reaction gas pipe 26.
Then, the sapphire substrate 24 was vapor-phase etched. Then the temperature
The temperature is lowered to 950 ° C, and 3 L / H ₂ is supplied from the first reaction gas pipe 25.
Min, NH ₃ at 2 l / min, TMA at 7 × 10 ^-6 mol / min and 1
Heat treated for minutes. By this heat treatment, the AlN buffer layer 30
Was formed to a thickness of about 0.1 μm. TMA after 1 minute
Supply of H ₂ is stopped, the temperature of the sapphire substrate 24 is maintained at 970 ° C., and H ₂ is fed from the first reaction gas pipe 25 at 2.5 l / min and NH ₃ at 1.5 l.
/ Min, TMG was supplied at 1.7 × 10 ⁻⁵ mol / min for 60 minutes to form an N layer 31 of N-type GaN having a film thickness of about 7 μm. next,
The sapphire substrate 24 is taken out of the reaction chamber 20, and the N layer 31
A photoresist having a predetermined pattern was obtained by applying a photoresist to the main surface of the substrate, exposing it using a mask having a predetermined pattern, and then performing etching. Next, using this photoresist as a mask, a SiO ₂ film 32 having a film thickness of about 100 Å was patterned.
Then, after removing the photoresist and cleaning the sapphire substrate 24 on which only the SiO ₂ film 32 is patterned, the susceptor is again used.
It was attached to 22 and vapor-phase etched. Then, the temperature of the sapphire substrate 24 is maintained at 970 ° C., and from the first reaction gas pipe 25, H ₂ is supplied at 2.5 l / min, NH ₃ is supplied at 1.5 l / min, and TMG is supplied at 1.7 × 10 ⁻⁵ mol / min. Then, from the second reaction gas pipe 26, DEZ is 5 × 10 ^-6
I layer composed of I-type GaN supplied at a mol / min for 5 minutes 33
To a film thickness of 1.0 μm. At this time, in the exposed portion of GaN, single crystal I-type GaN is grown to obtain an I layer 33, but a conductive layer 34 made of polycrystalline GaN is formed on the SiO ₂ film 32.
Is formed. Then, from the reaction chamber 20 to the sapphire substrate 24
The aluminum electrode on the I layer 33 and the conductive layer 34.
35 and 36 were vapor-deposited, and the sapphire substrate 24 was cut into a predetermined size to form a light emitting diode. in this case,
The electrode 35 becomes the electrode of the I layer 33, and the electrode 36 becomes the electrode of the N layer 31 via the conductive layer 34 and the extremely thin SiO ₂ film 32. And
By making the I layer 33 have a positive potential with respect to the N layer 31, light is emitted from the bonding surface. The third photomicrograph of the cross section of the I layer 33 grown on the N layer 31
Figure (a) shows the reflection diffraction method (RH
A photograph showing the results of EED) is shown in Fig. 4 (a). Also, S
A photomicrograph of the conductive layer 34 grown on the iO ₂ film 32 is shown in FIG. 3 (b), and a photo showing the result of RHEED is shown in FIG. 4 (b). As can be seen from these photographs, single-crystal GaN is grown on the N-type GaN, and polycrystalline GaN is grown on the SiO ₂ film. The polycrystalline GaN has higher conductivity than single-crystal I-type GaN, and becomes the conductive layer 34 and the lead for the N layer 31. Further, to form an Al _x Ga _1-x N based light emitting diode,
When forming the N layer 31 and the I layer 33, from the first reaction tube 25
It is sufficient to flow TMA at a predetermined ratio. For example, the first reaction gas pipe 2
5 while maintaining the temperature of the sapphire substrate 24 to 1105 ° C., H ₂ 3
l / min, NH ₃ 2 l / min, TMA 7.2 × 10 ⁻⁶ mol / min, TMG 1.7
× 10 was fed at ^-5 mol / min, than to feed at 5 × 10 ^-6 mol / min DEZ from the second reaction gas tubes 26, X = a 0.3 I-type Al _x Ga _1-x N based semiconductor A thin film is obtained.

【The invention's effect】

According to the present invention, a buffer layer is grown on a sapphire substrate of an N-type gallium nitride-based compound semiconductor, an N layer is formed on the buffer layer, and an extremely thin dioxide is formed so that a current flows on the main surface of the N layer. After patterning the silicon thin film, an I-type gallium nitride-based compound semiconductor is selectively grown using the silicon dioxide thin film as a mask to form a single crystal I layer,
A non-single-crystal conductive layer is formed on the silicon dioxide thin film. Therefore, the current from the N layer will pass through the extremely thin silico dioxide film and into the conductive layer. Therefore, it is possible to form electrodes to be joined to the surface of the conductive layer and the surface of the I layer, respectively, and it is possible to form the electrodes on the same surface, which has the effect of simplifying the manufacturing of the light emitting element. is doing.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a vapor phase growth apparatus according to a specific embodiment of the present invention. FIG. 2 is a configuration diagram showing a configuration of a light emitting diode manufactured by the device. FIG. 3 is a photograph showing a crystal structure of the GaN layer grown on the N layer and the SiO ₂ film by a microscope. Figure 4 shows growth on N layer and SiO ₂ film
A photograph showing the RHEED crystal structure of the GaN layer. FIG. 5 is a block diagram showing the structure of a conventional light emitting device. 20 ... Reaction chamber, 21 ... Quartz reaction tube, 22 ... Susceptor, 23 ... Control rod, 24 ... Sapphire substrate, 25 ... First reaction gas tube, 26 ... Second reaction gas tube, 27 ... First manifold, 28 ... 2 manifold, 30 ... buffer layer, 31 ... N layer, 32 ... SiO ₂ film, 33 ...
I layer, 34 ... Conductive layer, 35, 36 ... Electrode, H ... NH ₃ supply system, I ... Carrier gas supply system, J ... TMG supply system, K ... TMA supply system, L ... DEZ supply system

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Akasaki Furomachi, Chikusa-ku, Nagoya, Aichi (no address) Inside Nagoya University (72) Inventor Kazumasa Hiramatsu Furomachi, Chikusa-ku, Nagoya, Aichi (no address) Nagoya On-campus (72) Inventor Hiroshi Amano Furo-cho, Chikusa-ku, Nagoya, Aichi (No address) Inside Nagoya University (56) References JP 61-38875 (JP, B2) JP 60-16758 (JP, B2) )

Claims (2)

[Claims] 1. A sapphire substrate, a buffer layer formed on the sapphire substrate, and an N-type gallium nitride-based compound semiconductor (Al _x Ga _1-x N; X = 0) formed on the buffer layer. On the main surface of the N layer, a silicon dioxide (SiO ₂ ) thin film patterned so thin that an electric current can pass through the N layer, and the silicon dioxide thin film is patterned on the N layer. I-type gallium nitride-based compound semiconductor (Al _x Ga _1-x N; X) that is selectively grown by doping impurities into the N layer and is joined to the N layer
An I layer formed of a non-single-crystal conductive layer that is formed on the silicon dioxide thin film at the same time as the growth of the I layer and is bonded to the silicon dioxide thin film, the I layer, and the conductive layer. A gallium nitride-based compound semiconductor light-emitting device having an electrode layer to be bonded to the surface of each. 2. The silicon dioxide thin film has a thickness of about 100Å
The gallium nitride-based compound semiconductor light-emitting device according to claim 1, wherein