JP3727091B2 - Group 3 nitride semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor element in which an element layer having good crystallinity is obtained at a high growth rate.
[0002]
[Prior art]
Conventionally, a buffer layer is formed on a sapphire substrate, a base layer made of GaN is formed on the buffer layer to a thickness of 2 to 3 μm, and a heterojunction light-emitting layer made of AlGaInN is formed on the base layer. Devices are known. Each layer of the light emitting element is formed by metal organic compound vapor phase epitaxy (MOVPE).
[0003]
[Problems to be solved by the invention]
On the other hand, a molecular beam epitaxy method (MBE) having a good film thickness controllability is known as a thin film growth method.
The inventors of the present invention formed a light emitting element having the above structure by a molecular beam epitaxy method (MBE). However, the thickness of the base layer is required to be 2 to 3 μm, and it took a long time to grow the base layer having this thickness by MBE. Further, in order to improve the manufacturing speed of the device, it is necessary to increase the growth rate of the base layer of this thickness. However, if the growth rate is increased, the crystallinity of the base layer is lowered, and therefore the base layer is reduced. The crystallinity of the light emitting layer formed thereon was also lowered. As a result, an element with high emission luminance could not be obtained.
[0004]
The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a high-performance element at high speed.
[0005]
[Means for Solving the Problems]
In the present invention, the base layer is formed by metal organic compound vapor phase epitaxy (MOVPE), and the element layer is formed by molecular beam epitaxy (MBE) . As a result, the base layer can be formed at high speed with good crystallinity. As a result, the crystallinity of the element layer formed on the highly crystalline base layer is also high, and the film formation is performed by MBE, so the controllability of the film thickness is also high, and the high-performance element is high speed. Can be obtained at
[0006]
Furthermore, since it is made by forming the above thickness 2μm a group bottom layer, it is possible to improve the crystallinity of the element layer formed on the base layer and thereon.
Further, according to the second, third , fourth , and fifth inventions, a light emitting diode and a laser having a high light emission output can be obtained.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
First embodiment In Fig. 1, a light emitting diode 10 has a sapphire substrate 1, and a 500 サ フ ァ イ ア AlN buffer layer 2 is formed on the sapphire substrate 1. Of On the buffer layer 2, in turn, a film thickness of about 2.0 [mu] m, the electron concentration of 2 × 10 ¹⁸ / cm high carrier concentration comprising a silicon-doped GaN of ³ n ⁺ layer 3, the thickness 0.10 .mu.m, electron concentration 2 × 10 N layer 4 made of silicon-doped GaN of ¹⁸ / cm ³ , light-emitting layer 5 made of InGaN multiple quantum well with a total film thickness of about 0.07 μm, film thickness of about 0.2 μm, hole concentration 5 × 10 ¹⁷ / cm ³ , concentration P layer 61 made of Al _0.08 Ga _0.92 N doped with magnesium at 1 × 10 ²⁰ / cm ³ , with a film thickness of about 0.2 μm, hole concentration of 7 × 10 ¹⁷ / cm ³ , magnesium concentration of 2 × 10 ²⁰ / cm ³ A contact layer 62 made of magnesium-doped GaN is formed. On the contact layer 62, an electrode 7 made of Ni bonded to the layer 62 is formed. Further, a part of the surface of the high carrier concentration n ⁺ layer 3 is exposed, and an electrode 8 made of Ni bonded to the layer 3 is formed on the exposed portion. The n ⁺ layer 3 is a base layer, and the n layer 4, the light emitting layer 5, the p layer 61, and the contact layer 62 are element layers that function as elements.
[0008]
Next, a method for manufacturing the light emitting diode 10 having this structure will be described.
The buffer layer 2 and the high carrier concentration n ⁺ layer 3 of the light emitting diode 10 were manufactured by vapor phase growth using a metal organic compound vapor phase growth method (hereinafter referred to as “M0VPE”). The gases used in MOVPE are NH ₃ and carrier gas H ₂ or N ₂ , trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”) and trimethylaluminum (Al (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”). "TMA") and silane (SiH ₄ ).
[0009]
First, a single-crystal sapphire substrate 1 having a thickness of 100 to 400 μm whose main surface is a surface cleaned by organic cleaning and heat treatment is mounted on a susceptor mounted in a reaction chamber of an M0VPE apparatus. Next, the sapphire substrate 1 was vapor-phase etched at a temperature of 1100 ° C. while flowing H ₂ at normal pressure and a flow rate of 2 liter / min into the reaction chamber.
[0010]
Next, the temperature is lowered to 400 ° C., H ₂ is supplied at 20 liter / min, NH ₃ is supplied at 10 liter / min, and TMA is supplied at 1.8 × 10 ⁻⁵ mol / min. The thickness was formed. Next, the temperature of the sapphire substrate 1 is maintained at 1000 ° C., H ₂ is 20 liter / min, NH ₃ is 10 liter / min, TMG is 1.7 × 10 ⁻⁴ liter / min, diluted to 0.86 ppm with H ₂ gas. silane was supplied for 30 minutes at 20 × 10 ^-8 mol / min, forming a thickness of about 2 [mu] m, the electron concentration of 2 × 10 ¹⁸ / cm high carrier concentration n ⁺ layer 3 made of GaN doped with silicon of ³ did.
[0011]
Next, the substrate on which the above layers were laminated was mounted in the MBE apparatus. The temperature of the sapphire substrate 1 was maintained at 660 ° C., an n layer 4 made of GaN doped with silicon at a growth rate of 0.2 μm / h, a film thickness of about 0.1 μm, and a concentration of 2 × 10 ¹⁸ / cm ³ was formed.
[0012]
Thereafter, the temperature of the sapphire substrate 1 was maintained at 660 ° C., and a barrier layer 51 made of In _0.08 Ga _0.92 N having a thickness of about 10 nm was formed at a growth rate of 0.1 μm / h. Next, the temperature of the sapphire substrate 1 was kept the same, and a silicon film made of In _0.16 Ga _0.84 N with a film thickness of about 10 nm was added to a concentration of 5 × 10 ¹⁸ / cm ^{3 at} a growth rate of 0.1 μm / h. A well layer 52 was formed. By repeating such a procedure, as shown in FIG. 2, a light emitting layer 5 having a multi-quantum well structure in which barrier layers 51 and well layers 52 are alternately stacked in four layers and three layers, and has a total thickness of 70 nm. Formed.
[0013]
Subsequently, the p layer 61 made of magnesium (Mg) -doped Al _0.08 Ga _0.92 N having a growth rate of 0.2 μm / h and a film thickness of about 0.2 μm was formed while maintaining the temperature at 660 ° C. The p-layer 61 has a magnesium concentration of 5 × 10 ²⁰ / cm ³ and a hole concentration of 2 × 10 ¹⁸ / cm ³ .
[0014]
Subsequently, the temperature was maintained at 660 ° C., and a contact layer 62 made of magnesium (Mg) -doped GaN having a growth rate of 0.2 μm / h and a film thickness of about 0.2 μm was formed. The contact layer 62 has a magnesium concentration of 5 × 10 ²¹ / cm ³ and a hole concentration of 3 × 10 ¹⁸ / cm ³ .
[0015]
In this way, a wafer having a cross-sectional structure shown in FIG. 2 was obtained.
Next, as shown in FIG. 3, a SiO ₂ layer 9 having a thickness of 2000 mm was formed on the contact layer 62 by sputtering, and a photoresist 10 was applied on the SiO ₂ layer 9. Then, by photolithography, as shown in FIG. 3, on the contact layer 62, the photoresist 10 at the electrode formation site A ^{′ with} respect to the high carrier concentration n ⁺ layer 3 was removed. Next, as shown in FIG. 4, the SiO ₂ layer 9 not covered with the photoresist 10 was removed with a hydrofluoric acid etching solution.
[0016]
Next, the contact layer 62, the p layer 61, the light emitting layer 5, and the n layer 4 at portions not covered with the photoresist 10 and the SiO ₂ layer 9 are subjected to a degree of vacuum of 0.04 Torr, a high frequency power of 0.44 W / cm ² , and BCl _3. Gas was supplied at a rate of 10 ml / min for dry etching, followed by dry etching with Ar. In this step, as shown in FIG. 5, a hole A for extracting an electrode from the high carrier concentration n ⁺ layer 3 was formed.
[0017]
Next, Ni is uniformly vapor-deposited on the entire upper surface of the sample, and after applying a photoresist, a photolithography process, and an etching process, as shown in FIG. 1, the high carrier concentration n ⁺ layer 3 and the contact layer 62 are applied. Electrodes 8 and 7 were formed. Thereafter, the wafer processed as described above was cut into each chip to obtain a light emitting diode chip.
[0018]
The light-emitting element thus obtained had a drive current of 20 mA, an emission peak wavelength of 405 nm, and an emission intensity of 2 mW. This luminous efficiency was 3%. Compared with the case where all layers of the light emitting diode having the same structure as described above are formed by MBE, the light emission output is increased 10 ⁵ times.
[0019]
As described above, the present invention is characterized in that the base layer, which has a high crystallinity and needs to be formed thick, is formed at a high speed by the MOVPE method, and the element layer requiring control of the film thickness is formed by the MBE method. Therefore, since the base layer having high crystallinity can be obtained at high speed, the device manufacturing speed can be improved without lowering the crystallinity of the element layer thereon.
[0020]
In the above embodiment, GaN is used for the n layer 4, but n-conducting AlGaN may be used. Further, the p layer 61 may not be provided. Moreover, the period of the multiple quantum well structure of the light emitting layer 5 is arbitrary, and a single quantum well structure may be sufficient. InGaN is used for the well layer and the barrier layer, but a group III nitride semiconductor such as In _x Ga _y Al _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) is used. It may be used. Further, although silicon is added to the well layer, other donor impurities may be added or may not be added.
[0021]
Further, as shown in FIG. 6, the barrier layer 513 may be added without adding a donor impurity (for example, silicon) and an acceptor impurity (for example, zinc) only to the well layer 523. Further, as shown in FIG. 7, the barrier layer 510 may be added without adding a donor impurity (for example, silicon) and an acceptor impurity (for example, zinc) to the well layer 520 alternately. Further, as shown in FIG. 8, a donor impurity (eg, silicon) may be added to the well layer 521, and an acceptor impurity (eg, zinc) may be added to the barrier layer 511. An acceptor impurity may be added and a donor impurity may be added to the barrier layer 511. These features relating to the impurity distribution can change the emission wavelength. The well layer and the barrier layer may be n-type, p-type, or semi-insulating.
[0022]
Further, the light emitting layer 5 may be a multi-layer that does not have a quantum well structure by thickening each layer. In this case as well, the structures of FIGS. 6 to 7 can be considered. In this case, since attention is paid only to the distribution of impurities, the layers 513 and 523, the layers 510 and 520, and the layers 511 and 521 may have the same composition ratio. The above impurity distribution can change the emission wavelength. Also in this case, each layer of the light emitting layer 5 may be n-type, p-type, and semi-insulating.
[0023]
Furthermore, the light emitting layer 5 may be a single layer as shown in FIG. In the above embodiment, a sapphire substrate is used, but SiC, MgAl ₂ O ₄ or the like can be used. Further, although AlN is used for the buffer layer, AlGaN, GaN, InAlGaN, or the like can be used. Further, although GaN is used for the base layer, a group III nitride semiconductor such as In _x Ga _y Al _1-xy N can be used. Similarly, a group III nitride semiconductor such as In _x Ga _y Al _1-xy N having an arbitrary composition ratio can be used for the element layer. When grown by MBE, it can be made p-type without heat treatment, but heat treatment may be added after growth.
[0024]
In addition to the light emitting diode, the present invention can be applied to laser diodes in the blue and ultraviolet regions, light detection elements, and other functional elements.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating 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 example.
FIG. 3 is a cross-sectional view showing a manufacturing process of the light-emitting diode of the example.
FIG. 4 is a cross-sectional view showing a manufacturing process of the light-emitting diode of the same example.
FIG. 5 is a cross-sectional view showing a manufacturing process of the light-emitting diode of the example.
FIG. 6 is a cross-sectional view showing another structure of the light emitting layer.
FIG. 7 is a cross-sectional view showing another structure of the light emitting layer.
FIG. 8 is a cross-sectional view showing another structure of the light emitting layer.
FIG. 9 is a configuration diagram illustrating a configuration of a light emitting diode according to another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Light emitting diode 1 ... Sapphire substrate 2 ... Buffer layer 3 ... High carrier concentration n ^<+> layer 4 ... n layer 5 ... Light emitting layer 61 ... p layer 62 ... Contact layer 7, 8 ... Electrode

Claims (5)

A semiconductor having a substrate, a buffer layer formed on the substrate, a base layer made of a group III nitride semiconductor formed on the buffer layer, and an element layer made of a group III nitride semiconductor formed on the base layer In the element
The base layer is a layer formed by metal organic compound vapor deposition (MOVPE),
The base layer is formed to a thickness of 2 μm or more,
The group III nitride semiconductor device, wherein the device layer is a layer formed by molecular beam epitaxy (MBE). 2. The group III nitride according to claim 1 , wherein the base layer is made of GaN and the element layer is a light emitting element having at least a p layer and an n layer made of a group 3 nitride semiconductor. Semiconductor element. 2. The group III nitride semiconductor device according to claim 1 , wherein the device layer includes a p-layer, an n-layer, and a light-emitting layer having a quantum well structure interposed therebetween. The group III nitride semiconductor device according to claim 2 , wherein the substrate is a sapphire substrate. 3 nitride semiconductor device according to claim 2 wherein the buffer layer is characterized by the AlN der Turkey.

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