JP3712770B2 - Method for manufacturing group 3 nitride semiconductor and semiconductor device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a light emitting device using a group 3 nitride semiconductor.
[0002]
[Prior art]
Conventionally, a blue laser diode having a structure in which a buffer layer is formed on a sapphire substrate and an AlGaInN based compound semiconductor double heterojunction is formed on the buffer layer is known. Since the compound semiconductor is a direct transition type, it has been attracting attention because of its high luminous efficiency and the fact that one of the three primary colors of light is blue.
[0003]
[Problems to be solved by the invention]
However, although the conventional laser diode having the above structure uses a buffer layer, an AlGaInN-based compound semiconductor is grown on a substrate of a different material, so that the crystallinity is still not good. That is, this lattice defect penetrates perpendicularly from the substrate surface to the light emitting layer, and the lattice defect density in the light emitting layer is about 10 ⁹ to 10 ¹⁰ / cm ² . The high density of lattice defects reduces the light emission efficiency and shortens the operating life.
The present invention has been made to solve the above-mentioned problems, and its object is to improve the crystallinity of an AlGaInN-based compound semiconductor grown on a foreign material substrate, and to improve the semiconductor element using the compound semiconductor. It is to improve the characteristics.
[0004]
[Means for Solving the Problems]
The present invention relates to a method for growing a group III nitride semiconductor (including Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0) on a substrate of a different material. A buffer layer formed with Al _x1 Ga _Y1 In _1-X1-Y1 N (0 ≦ X1 ≦ 1, 0 ≦ Y1 ≦ 1, 0 ≦ X1 + Y1 ≦ 1) at a temperature at which the single crystal does not grow on the single crystal, A _{single layer} of Al _x2 Ga _Y2 In _1-X2-Y2 N (including 0 ≦ X2 ≦ 1, 0 ≦ Y2 ≦ 1, 0 ≦ X2 + Y2 ≦ 1, X1 = X2, Y1 = Y2) at the growth temperature Three or more crystal layers are alternately stacked, and the target Al _x3 Ga _Y3 In _1-X3-Y3 N (0 ≦ X3 ≦ 1, 0 ≦ Y3 ≦ 1, 0 at the temperature at which the single crystal grows on it. ≦ X3 + Y3 ≦ 1, X1 or X2 = X3, Y1 or Y2 = Y3 is included). Another feature of the present invention is a semiconductor device in which the Al _x3 Ga _Y3 In _1-X3-Y3 N layer thus formed is used as a base layer of the device layer.
[0005]
With this configuration, lattice defects extending vertically from the substrate surface are interrupted in the middle by repetition of the buffer layer and the single crystal layer, and do not reach the target single crystal layer. In particular, dislocations from the substrate surface are confined to 50 to 1000 mm of the single crystal of the buffer layer and are prevented from propagating to the upper layer. Therefore, the density of lattice defects in the semiconductor layer for forming the element is reduced, and a single crystal semiconductor made of high-quality Al _x3 Ga _Y3 In _1-X3-Y3 N can be obtained on a substrate made of a different material. Further, in the case where an element is formed using the single crystal semiconductor as a base layer, the crystallinity of the layer in which the element is formed becomes high, and the characteristics of the element can be improved. In particular, when a light emitting element is formed, light emission efficiency, element life, and light emission luminance can be improved.
[0006]
As in claim 1, 5, 100 to 1000 Å the thickness of the buffer layer, the thickness of the single crystal layer by a 500 to 3000 Å, also as of claim 2, 6, the growth temperature of the buffer layer By setting the temperature to 350 to 800 ° C., it is possible to efficiently prevent the lattice defects from extending from the substrate surface to the target semiconductor layer.
Further, if the thickness of the single crystal layer exceeds 3000 mm, the distortion becomes undesirably large.
[0007]
Buffer layer and the single crystal layer has the general formula _{Al x Ga Y In 1-XY} N 4, ternary, can be a binary nitride semiconductor. In particular, as claimed in claim 3, a buffer layer AlN, a single crystal layer by the GaN, it is possible to greatly reduce the lattice defect density of the GaN layer of interest. In addition, sapphire or SiC can be used for the substrate.
Note that the number of repetitions of the buffer layer and the single crystal layer is arbitrary.
Further, it is preferable from the standpoint of crystallinity of the single crystal and the simplicity of the process that the temperature is increased as it is after the last buffer layer formation to grow the single crystal layer.
[0008]
【Example】
The target layer of Al _x3 Ga _Y3 In _1-X3-Y3 N was formed on the sapphire substrate as follows. Each layer was formed by vapor phase growth using an organic metal compound vapor phase growth method (hereinafter referred to as “M0VPE”).
The gases used were 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 “TMA”). ”).
[0009]
First, a single crystal sapphire substrate 1 having a thickness of 100 to 400 μm 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, and as shown in FIG. The buffer layer 21 was formed to a thickness of about 500 mm. Next, the temperature of the sapphire substrate 1 is maintained at 1150 ° C., H ₂ is supplied at 20 liter / min, NH ₃ is supplied at 10 liter / min, and TMG is supplied at 1.7 × 10 ⁻⁴ mol / min to obtain a film thickness of about 0.3 A single crystal layer 31 made of μm GaN was formed.
[0011]
Next, the temperature of the sapphire substrate 1 was lowered again to 400 ° C., and a buffer layer 22 made of AlN having a thickness of 500 mm was formed under the same conditions as the formation of the buffer layer 21. Next, the temperature of the sapphire substrate 1 was again raised to 1150 ° C., and a single crystal layer 32 made of GaN having a thickness of 0.3 μm was formed under the same conditions as the formation of the single crystal layer 31. Further, the temperature of the sapphire substrate 1 was lowered again to 400 ° C., and the buffer layer 23 was similarly formed on the single crystal layer 32. Then, the temperature of the sapphire substrate 1 was again raised to 1150 ° C., and the target single crystal layer 33 made of GaN having a thickness of 1.5 μm was formed under the same conditions as the formation of the single crystal layer 31.
[0012]
This single crystal layer 33 was etched with KOH, and the dislocation density on the surface was measured with an electron scanning microscope by the etch pit method. The result was 8 × 10 ⁵ cm ² . As in the prior art, when the buffer layer 22 made of one layer of AlN is formed on the sapphire substrate 1 and the single crystal layer made of the target GaN is formed thereon, the etch pit density is 4 × 10 ⁷ / cm. ^2, so the manufacturing method of this embodiment, the etch pit density was reduced to 1/50.
[0013]
The reason why the etch pits can be reduced by making the buffer layer a multi-layer structure is considered as follows. The shape of the pit is a hexagon when observed with an electron microscope. The initial growth of GaN formed on the AlN buffer layer is hexagonal island crystals. After that, the buffer layer is covered with GaN as the crystal grows, but it is thought that the lattice defect part is left and becomes hexagonal pits. However, the AlN buffer layer and the single crystal layer of GaN have a multi-periodic structure, so the AlN layer interferes well with the GaN layer and the lattice defects are blocked.
[0014]
In the above embodiment, AlN is used for the buffer layer, but other binary GaN, InN, ternary AlGaN, InGaN, quaternary AlGaInN, or the like can be used. In this case, the buffer layer is formed at a low temperature at which the single crystal does not grow, and the thickness is preferably 100 to 1000 mm. The material of the single crystal layer formed on the buffer layer may be the same as the buffer layer and the material and the composition ratio, or may be a different material or the same material and the composition ratio may be different. In addition to GaN, ternary AlGaN and InGaN having an arbitrary composition ratio and quaternary AlGaInN having an arbitrary composition ratio can be used for the single crystal layer. The growth temperature of the single crystal layer is a temperature at which the single crystal can be grown. Generally, the thickness is preferably in the range of 500 to 3000 mm. The number of repetitions of the buffer layer and the single crystal layer is arbitrary.
[0015]
Further, the target single crystal semiconductor layer is a binary, ternary or quaternary group III nitride semiconductor Al _x3 Ga _Y3 In _1-X3-Y3 N (0 ≦ X3 ≦ 1, 0 ≦ Y3 ≦ 1 , 0 ≦ X3 + Y3 ≦ 1).
[0016]
Next, the laser diode 10 was manufactured using this manufacturing method.
In FIG. 1, a laser diode 10 has a sapphire substrate 1, and an intermediate layer 2 is formed on the sapphire substrate 1. The intermediate layer 2 has the same structure as that shown in FIG. That is, the intermediate layer 2 includes a buffer layer 21 made of AlN having a thickness of 500 mm, a single crystal layer 31 made of 0.3 μm thick, a buffer layer 22 made of AlN having a thickness of 500 mm, and a single crystal layer 32 made of 0.3 μm thick. The buffer layer 23 is made of a multi-layer structure of 500 Al AlN.
[0017]
Then, the on the intermediate layer 2, in turn, the electron concentration of 2 × 10 ¹⁸ / cm high carrier concentration comprising a silicon-doped GaN of ³ n ⁺ layer 3, silicon-doped electron concentration of 2 × 10 ¹⁸ / cm ³ AlGaN An n-conducting clad layer 4, an active layer 5 made of InGaN having a thickness of about 0.05 μm, and a hole concentration of 1 × 10 ¹⁸ / cm ³ and a concentration of 2 × 10 ²⁰ / cm ³ of AlGaN doped with magnesium. A p-conduction type clad layer 61, a contact layer 62 made of magnesium-doped GaN having a hole concentration of 1 × 10 ¹⁸ / cm ³ and a magnesium concentration of 2 × 10 ²⁰ / cm ³ are formed. An SiO ₂ layer 9 is formed on the contact layer 62, and an electrode 7 made of Ni that is bonded to the contact layer 62 through a window portion of the SiO ₂ layer 9 is formed. Furthermore, an electrode 8 made of Ni bonded to the layer 3 is formed on the high carrier concentration n ⁺ layer 3.
[0018]
Next, a method for manufacturing the laser diode 10 having this structure will be described.
The laser diode 10 was manufactured by vapor phase growth using M0VPE.
The gases used were NH ₃ and carrier gas H ₂ or N ₂ , TMG, TMA, trimethylindium (In (CH ₃ ) ₃ ) (hereinafter referred to as “TMI”), silane (SiH ₄ ) and cyclopentadidiene. Enilmagnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter referred to as “CP ₂ Mg”).
[0019]
First, a single crystal sapphire substrate 1 having a thickness of 100 to 400 μm 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.
[0020]
Next, the temperature is lowered to 400 ° C., and 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, so that the buffer layer 21 of AlN is about 500 mm. The thickness was formed. Next, the temperature of the sapphire substrate 1 is maintained at 1150 ° C., H ₂ is supplied at 20 liter / min, NH ₃ is supplied at 10 liter / min, and TMG is supplied at 1.7 × 10 ⁻⁴ liter / min for 4 minutes to form a film. A single crystal layer 31 made of GaN having a thickness of about 0.3 μm was formed.
[0021]
Next, the temperature of the sapphire substrate 1 was lowered again to 400 ° C., and a buffer layer 22 made of AlN having a thickness of 500 mm was formed under the same conditions as the formation of the buffer layer 21. Next, the temperature of the sapphire substrate 1 was again raised to 1150 ° C., and a single crystal layer 32 made of GaN having a thickness of 0.3 μm was formed under the same conditions as the formation of the single crystal layer 31. Further, the temperature of the sapphire substrate 1 was lowered again to 400 ° C., and the buffer layer 23 was similarly formed on the single crystal layer 32.
[0022]
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 is 1.7 × 10 ⁻⁴ liter / min, and diluted to 0.86 ppm with H ₂ gas. The supplied silane was supplied at 200 ml / min to form a high carrier concentration n ⁺ layer 3 made of silicon-doped GaN having a film thickness of about 2.2 μm and an electron concentration of 2 × 10 ¹⁸ / cm ³ .
[0023]
Next, the temperature of the sapphire substrate 1 is maintained at 1100 ° C., N ₂ or H ₂ is 10 liter / min, NH ₃ is 10 liter / min, TMG is 1.12 × 10 ⁻⁴ mol / min, and TMA is 0.47 × 10. ^-4 mol / min and n-conductivity composed of silicon-doped AlGaN with a concentration of 2 × 10 ¹⁸ / cm ³ by supplying silane diluted to 0.86 ppm with H ₂ gas at 10 × 10 ^-9 mol / min A mold cladding layer 4 was formed.
[0024]
Subsequently, the temperature is maintained at 850 ° C., N ₂ or H ₂ is 20 liter / min, NH ₃ is 10 liter / min, TMG is 1.53 × 10 ⁻⁴ mol / min, and TMI is 0.02 × 10 ^−4. The active layer 5 made of 0.05 μm InGaN was formed by supplying at a mol / min.
[0025]
Subsequently, the temperature is maintained at 1100 ° C., N ₂ or H ₂ is 20 liter / min, NH ₃ is 10 liter / min, TMG is 1.12 × 10 ⁻⁴ mol / min, and TMA is 0.47 × 10 ⁻⁴ mol / min. Then, CP ₂ Mg was supplied at 2 × 10 ⁻⁴ mol / min to form a p-conductivity type cladding layer 61 made of magnesium (Mg) -doped AlGaN. The concentration of magnesium in the cladding layer 61 is 2 × 10 ²⁰ / cm ³ . In this state, the clad layer 61 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.
[0026]
Subsequently, the temperature is maintained at 1100 ° C., N ₂ or H ₂ is 20 liter / min, NH ₃ is 10 liter / min, TMG is 1.12 × 10 ⁻⁴ mol / min, and CP ₂ Mg is 4 × 10. ^The contact layer 62 made of GaN doped with magnesium (Mg) and having a thickness of about 0.2 μm was formed at a ^{rate of −4} mol / min. The concentration of magnesium in the contact layer 62 is 2 × 10 ²⁰ / cm ³ . In this state, the contact layer 62 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.
[0027]
Next, by electron beam irradiation, the contact layer 62 and the cladding layer 61 became p-conductivity type semiconductors having a hole concentration of 1 × 10 ¹⁸ / cm ³ and a resistivity of 2 Ωcm. In this way, a wafer having a multilayer structure was obtained.
[0028]
Next, a SiO ₂ layer 9 having a thickness of 2000 mm was formed on the contact layer 62 by sputtering, and a photoresist was applied on the SiO ₂ layer 9. Then, the photoresist at the electrode formation site with respect to the high carrier concentration n ⁺ layer 3 was removed on the contact layer 62 by photolithography. Next, the SiO ₂ layer 9 not covered with the photoresist was removed with a hydrofluoric acid etching solution.
[0029]
Next, the contact layer 62, the clad layer 61, the active layer 5 and the clad layer 4 at portions not covered with the photoresist and the SiO ₂ layer 9 are subjected to a vacuum degree of 0.04 Torr, a high frequency power of 0.44 W / cm ² , and a BCl ₃ gas. Was supplied at a rate of 10 ml / min for dry etching and then dry etching with Ar. In this step, a hole A for extracting an electrode for the high carrier concentration n ⁺ layer 3 was formed.
[0030]
Next, a photoresist was applied to the SiO ₂ layer 9, a photolithography process, and wet etching were performed, and a window was formed in the electrode formation portion of the contact layer 62 of the SiO ₂ layer 9.
[0031]
Next, Ni was uniformly deposited on the entire upper surface of the sample, and electrodes 8 and 7 for the high carrier concentration n ⁺ layer 3 and the contact layer 62 were formed through a photoresist coating, a photolithography process, and an etching process. . Thereafter, the wafer processed as described above was cut into strips in the length direction of the laser cavity and cleaved at right angles to the direction to form a laser diode chip.
[0032]
In this way, the intermediate layer 2 is formed as a multiple layer of buffer layers made of low-temperature grown AlN, so that the crystallinity of the high carrier concentration n ⁺ layer 3, the cladding layer 4, the active layer 5, the cladding layer 61, and the contact layer 62 can be improved. I was able to improve.
[0033]
The intermediate layer 2 may be variously modified as shown in the examples of the manufacturing method. In the above embodiment, the structure of the active layer 5 is a single layer of InGaN. However, a multiple quantum well structure composed of InGaN and GaN each having a thickness of 100 mm may be used. The thickness of the active layer 5 is 100 to 1000 mm.
In the present embodiment, the laser diode has been described, but it goes without saying that it can be applied to various GaN-based electronic devices including optical elements such as a light emitting diode and a light receiving element.
[0034]
Further, the cladding layer 4, 61, the active layer 5 is generally may be _{Al x Ga y In 1-xy} N. The composition ratio x: y: 1-xy is determined according to the oscillation wavelength of the laser.
[0035]
The p-type can be formed by electron beam irradiation, heat treatment, heat treatment in N ₂ plasma gas, or laser irradiation.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a semiconductor layer illustrating a manufacturing method according to a specific embodiment of the present invention.
FIG. 2 is a configuration diagram showing the configuration of a laser diode according to a specific embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Laser diode 1 ... Sapphire substrate 2 ... Intermediate layers 21, 22, 23 ... Buffer layers 31, 32 ... Single crystal layer 3 ... High carrier concentration n ⁺ layer 4 ... Cladding layer 5 ... Active layer 61 ... Cladding layer 62 ... Contact Layers 7, 8 ... electrode 9 ... SiO ₂ layer

Claims (9)

In a method of growing a group III nitride semiconductor (Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0) on a substrate of a different material,
Al _x1 Ga _Y1 In _1-X1-Y1 N (0 ≦ X1 ≦ 1, 0 ≦ Y1 ≦ 1, 0 ≦ X1 + Y1 ≦ 1) formed at a temperature at which a single crystal does not grow on the substrate 100 to 100 and 1000Å buffer _{layer, Al x2 Ga Y2 in 1-} X2-Y2 N (0 ≦ X2 ≦ 1 at a temperature single crystal is grown, 0 ≦ Y2 ≦ 1, 0 ≦ X2 + Y2 ≦ 1, X1 = X2, Y1 Three or more single crystal layers having a thickness of 500 to 3000 mm, which are formed at a temperature at which the single crystal grows on the target Al _x3 Ga _Y3 In _1-X3-Y3 Group III nitride characterized by forming a layer of N (including 0 ≦ X3 ≦ 1, 0 ≦ Y3 ≦ 1, 0 ≦ X3 + Y3 ≦ 1, X1 or X2 = X3, Y1 or Y2 = Y3) A method for manufacturing a semiconductor.   The method for producing a group III nitride semiconductor according to claim 1, wherein the growth temperature of the buffer layer is 350 to 800 ° C.   2. The method for producing a group III nitride semiconductor according to claim 1, wherein the buffer layer is AlN and the single crystal layer is GaN.   2. The method for producing a group III nitride semiconductor according to claim 1, wherein the substrate is sapphire or SiC. In a semiconductor device using a group III nitride semiconductor (Al _x Ga _Y In _1-XY N; including X = 0, Y = 0, X = Y = 0) formed on a substrate of a different material as an element layer,
Between the substrate and the element layer,
Thickness formed of Al _x1 Ga _Y1 In _1-X1-Y1 N (0 ≦ X1 ≦ 1, 0 ≦ Y1 ≦ 1, 0 ≦ X1 + Y1 ≦ 1) formed at a temperature at which no single crystal grows on the substrate Al _x2 Ga _Y2 In _1-X2-Y2 N (0 ≦ X2 ≦ 1, 0 ≦ Y2 ≦ 1, 0 ≦ X2 + Y2 ≦ 1, formed with a buffer layer of 100 to 1000 mm and a temperature at which a single crystal grows A semiconductor element characterized in that an intermediate layer in which three or more single crystal layers having a thickness of 500 to 3000 積 層 are alternately stacked is interposed between X1 = X2 and Y1 = Y2. The semiconductor element according to claim 5 , wherein the growth temperature of the buffer layer is 350 to 800 ° C. 6. The semiconductor device according to claim 5 , wherein the buffer layer is AlN and the single crystal layer is GaN. The semiconductor device according to claim 5 , wherein the substrate is sapphire or SiC. The semiconductor element according to claim 5 , wherein the element layer is a base layer of an optical element.

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