JP2004063519A - Chemical vapor deposition method of group iii nitride semiconductor layer and group iii nitride semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chemical vapor deposition method of boron phosphide semiconductor layer and group III nitride semiconductor layer for easily forming the group III nitride semiconductor layer having good crystalline property in order to form, with the vapor phase growth method, the gourp III nitride semiconductor layer on the boron phosphide layer provided on a silicon single crystal substrate. <P>SOLUTION: First, an amorphous layer including boron and phosphorus which has a function to relax lattice mismatch between silicon single crystal and boron phosphide crystal layer is formed with the vapor phase growth method on the surface of a silicon (Si) single crystal substrate. Thereafter, the boron phosphide crystal layer is formed with the vapor phase deposition method by varying the the concentration of boron atoms supplied from the vapor phase deposition region and the supply concentration ratio of phosphorus source to the boron source (V/III ratio) within the unit period. Moreover, the group III nitride semiconductor layer is also formed with the vapor phase deposition method at the temperature for suppressing thermal modification property of the boron phosphide crystal layer. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a group III nitride including a boron (phosphide) layer grown on a silicon (Si) single crystal substrate as an underlayer, and a highly volatile component such as gallium (Ga) or indium (In) formed thereon. The present invention relates to a method for suitably vapor-phase growing a semiconductor layer and a group III nitride semiconductor device manufactured by the method.
[0002]
[Prior art]
Aluminum nitride, gallium, indium (Al _X Ga _Y In _1-XY N: 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ X + Y ≦ 1 or gallium nitride phosphide (GaN _1-Z P _Z : 0 ≦ Z ≦ 1), for example, a light emitting diode (LED) that emits near-ultraviolet light or short-wavelength visible light, such as an active layer (light emitting layer) or a barrier (cladding). (1) Japanese Patent Publication No. 55-3834, and (2) "III-nitride semiconductor" (Baifukan Co., Ltd., first edition issued on December 8, 1999), 241-255. Page). In addition, for example, it is used as an active (channel) layer, a spacer (spacer) layer, an electron supply layer, or the like of a Schottky junction field effect transistor (MESFET) that operates in a high frequency band (the above-mentioned “Group III”). Nitride semiconductor ", pp. 285-294).
[0003]
For example, when a light emitting element such as an LED or a laser diode (LD) is described as an example, recently, a conductive silicon (Si) single crystal is used as a substrate because of an advantage that an ohmic electrode can be easily arranged. (See Electron. Lett., 33 (23) (1997), 1986-1987). However, the degree of lattice mismatch between silicon single crystal (silicon) and, for example, gallium nitride reaches as high as about 17% (see Electron. Lett., 33 (1997) above). In order to alleviate the lattice mismatch, the prior art employs a means for vapor-phase growing a gallium nitride layer via a boron phosphide (BP) layer provided on a silicon single crystal substrate (" 26, No. 2 (1999), p. 29). Since the lattice constant of a cubic boron phosphide single crystal of zincblende crystal type (zincblend) is about 0.454 nm (Iwao Teramoto, "Introduction to Semiconductor Devices", Baifukan Co., Ltd., March 30, 1995) First publication), p. 28), and good lattice matching is obtained with the lattice constant (0.451 nm) of cubic gallium nitride.
[0004]
On the other hand, the degree of lattice mismatch between boron phosphide and silicon single crystal is also as large as about 16% (refer to the above-mentioned "Journal of Japan Society for Crystal Growth", Vol. 26 (1997)). For this reason, when the boron phosphide layer is grown on a silicon single crystal substrate in a vapor phase, a boron phosphide layer formed at a relatively low temperature and a boron phosphide crystal layer formed at a higher temperature are laminated. Technical means for providing a buffer layer have been invented (see US Pat. No. 6,069,021). In particular, a boron phosphide layer made of amorphous (amorphous) which has been grown at a relatively low temperature in a vapor phase can reduce the lattice mismatch between the silicon single crystal and the boron phosphide crystal layer of the substrate to provide high quality phosphide. The effect of providing a boron crystal layer has been proposed (see the above-mentioned US Pat. No. 6,069,021). In recent years, in order to obtain an amorphous boron phosphide layer stably, the concentration ratio of the boron source and the phosphorus source supplied to the region where the vapor phase deposition reaction occurs, that is, the so-called V / III ratio, is set to a suitable range. There is also proposed a vapor phase growth means having a content defined in the following.
[0005]
[Problems to be solved by the invention]
In order to relax the lattice mismatch and deposit a group III nitride semiconductor layer having few crystal defects such as misfit dislocations on the boron phosphide layer, it is necessary to keep the V / III ratio within a suitable range. In addition, other conditions had to be precisely defined. The present invention can easily provide a group III nitride semiconductor layer having good crystallinity when a group III nitride semiconductor layer is vapor-phase grown on a boron phosphide layer provided on a silicon single crystal substrate. A method for vapor-phase growth of a boron phosphide semiconductor layer and a group III nitride semiconductor layer is provided. Further, according to the vapor deposition method according to the present invention, a semiconductor element having a group III nitride semiconductor layer having good crystallinity formed on a silicon (Si) single crystal substrate via a boron phosphide layer is provided. provide.
[0006]
[Means for Solving the Problems]
That is, the present invention
(1) The temperature T is applied to the surface of a silicon (Si) single crystal substrate. ₁ (Unit: ° C) (However, 250 ° C ≤ T ₁ .Ltoreq.1200.degree. C.), the first ratio of the concentration of the phosphorus source to the concentration of the boron source supplied to the vapor phase growth region per unit time (hereinafter referred to as V / III ratio) of 0.2 to 40. A first step of vapor-phase growing an amorphous layer containing boron (B) and phosphorus (P) with the concentration of boron atoms supplied from a boron source in a unit time as a first concentration;
On the amorphous layer, a temperature T ₂ (Unit: ° C) (However, 750 ° C ≤ T ₂ ≦ 1200 ° C.), the V / III ratio is a second ratio equal to or higher than the first ratio, and the concentration of boron atoms supplied from the boron source within a unit time is a second concentration equal to or lower than the first concentration. A second step of vapor-phase growing a boron phosphide (BP) crystal layer;
On the boron phosphide crystal layer, T ₂ Below and temperature T above 250 ° C ₃ (Unit: ° C) (However, 250 ° C ≤ T ₃ ≤T ₂ ), A third step of vapor-phase growing the group III nitride semiconductor layer;
A method for vapor-phase growing a group III nitride semiconductor layer, comprising:
(2) The method of (1) above, wherein the thickness of the amorphous layer is 1 nm or more and 50 nm or less.
(3) In the second step, the boron phosphide crystal layer has a V / III ratio of 1.5 × 10 ² 1 x 10 ⁴ The vapor phase growth method for a group III nitride semiconductor layer according to the above (1) or (2), wherein the vapor phase growth is performed in the following range.
(4) Temperature T at which the boron phosphide (BP) crystal layer is vapor-phase grown in the second step. ₂ At the temperature T at which the amorphous layer is vapor-phase grown in the first step. ₁ The method for vapor-phase growing a group III nitride semiconductor layer according to any one of the above (1) to (3), wherein the temperature is set as follows.
(5) The second concentration, which is the concentration of boron atoms supplied in the second step, is 1/30 of the first concentration, which is the concentration of boron atoms supplied in the first step. The method for vapor-phase growing a group III nitride semiconductor layer according to any one of the above (1) to (4), wherein the thickness is set to 1/5 or less.
(6) The first concentration, which is the concentration of boron atoms supplied in the first step, is 1 × 10 ^-6 4 × 10 at more than mol / min ^-5 Mol / min or less, and the second concentration, which is the concentration of boron atoms supplied in the second step, is 3.3 × 10 3 ^-8 8 × 10 over mol / min ^-6 (5) The vapor phase growth method of a group III nitride semiconductor layer according to the above (5), wherein the molar ratio is not more than mol / min.
(7) In the third step, the group III nitride semiconductor layer is formed such that the V / III ratio is 1 × 10 ⁴ ~ 5 × 10 ⁴ (1) to (6), wherein the group III nitride semiconductor layer is vapor-phase grown.
I will provide a.
[0007]
Also, the present invention
(8) According to the method of vapor-phase growing a group III nitride semiconductor layer according to any one of the above (1) to (7), boron (B) and phosphorus are added to the surface of the silicon (Si) single crystal substrate. A group III nitride semiconductor device manufactured by sequentially vapor-phase growing an amorphous layer containing (P), a boron phosphide crystal layer, and a group III nitride semiconductor layer.
I will provide a.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the amorphous layer containing boron (B) and phosphorus (P), the boron phosphide crystal layer, and the group III nitride semiconductor layer, which are sequentially formed on the surface of the silicon single crystal substrate, are halogen. Vapor growth is performed by means such as a (hologen) method, a hydride method, a molecular beam epitaxy (MBE) method, and a metal organic chemical vapor deposition (MOCVD) method. The crystal plane of the surface of the silicon single crystal used as the substrate is preferably composed of {100}, {110}, or {111}, or an off-cut crystal plane thereof. In the present invention, first, a temperature T of not less than 250 ° C. and not more than 1200 ° C. ₁ An amorphous layer containing boron and phosphorus is formed on the surface of the silicon crystal substrate heated by using the above-described vapor phase growth means. For example, triethyl boron ((C ₂ H ₅ ) ₃ B) as a boron source and phosphine (PH ₃ ) Is formed using a normal pressure (substantially atmospheric pressure) or a reduced pressure MOCVD method using a phosphorus source. At a low temperature of less than 250 ° C., thermal decomposition of a boron source or a phosphorus source does not sufficiently proceed, so that an amorphous layer cannot be stably obtained. On the other hand, vapor phase growth at a high temperature exceeding 1200 ° C. ₁₃ P ₂ Etc. (see J. Am. Ceramic Soc., 47 (1) (1964), pp. 44-46), and it is easy to obtain a polycrystalline layer composed of boron and phosphorus. It is not preferable to obtain a stable quality layer.
[0009]
Silicon dioxide (SiO 2) that interferes with the vapor phase growth of the amorphous phase containing boron and phosphorus ₂ ) Or silicon nitride (Si ₃ N ₄ ), The amorphous layer is made of oxygen (O 2). ₂ ) Or nitrogen (N ₂ It is suitable to carry out vapor phase growth in an atmosphere containing no). Hydrogen (H ₂ An atmosphere or a mixed atmosphere of hydrogen and a monoatomic inert gas such as argon (Ar) can also be suitably used. It is desirable that the thickness of the amorphous layer containing boron and phosphorus is not less than 1 nanometer (unit: nm) and not more than 50 nm. An ultrathin film having a thickness of less than 1 nm does not sufficiently and uniformly cover the surface of the silicon crystal substrate. When the thickness exceeds 50 nm, it becomes impossible to stably obtain an amorphous layer having excellent surface flatness. Furthermore, the preferred thickness of the amorphous layer is generally between 5 nm and 20 nm. The thickness of the amorphous layer is controlled by adjusting the supply time of the boron source to the vapor phase growth region. The thickness of the amorphous layer can be measured, for example, by a cross-sectional TEM technique using a transmission electron microscope (TEM). Further, by using an electron beam diffraction technique or an X-ray diffraction technique, it is possible to investigate the morphology of the crystals constituting the amorphous layer.
[0010]
When the amorphous layer containing boron and phosphorus is vapor-phase grown, the ratio of the concentration of the phosphorus source to the concentration of the boron source supplied per unit time to the vapor-phase growth region where the vapor-phase deposition reaction is performed, so-called V / It is preferable that the III ratio is a first ratio of 0.2 or more and 40 or less. The V / III ratio is the ratio of the concentration of phosphorus atoms in the phosphorus source to the concentration of boron atoms in the boron source supplied to the vapor phase growth region in a unit time. In a boron source or a phosphorus source containing only a boron or phosphorus atom, respectively, the V / III ratio can be represented by a ratio of a flow rate of a phosphorus source to a flow rate of a boron source supplied in a unit time. For example, the boron source triethylboron ((C ₂ H ₅ ) ₃ B) at a flow rate of 0.03 cc / min and a phosphine (PH ₃ ) Is supplied at a flow rate of 230 cc / min, the V / III ratio is about 7.7 × 10 ³ Is calculated. That is, the V / III ratio is adjusted by controlling the flow rates of the boron source and the phosphorus source supplied to the vapor phase growth region. The flow rate of the boron source or the phosphorus source can be precisely controlled by using, for example, an electronic mass flow meter (MFC).
[0011]
The amorphous layer having a layer thickness in the above-mentioned preferred range, which is formed by vapor-phase growth while controlling the V / III ratio to a first ratio of 0.2 or more and 40 or less, reduces lattice mismatch with a silicon single crystal. And can contribute to providing a high-quality boron phosphide crystal layer having a low density of crystal defects such as misfit dislocations. Furthermore, by defining the supply amount of the boron source to the vapor-phase growth region per unit time while keeping the V / III ratio within the above-mentioned preferable range, it is possible to provide an effect of alleviating lattice mismatch, and An amorphous layer having excellent surface flatness can be vapor-phase grown. For example, the concentration of the boron source supplied to the vapor deposition region in one minute is 1 × 10 ^-6 4 × 10 at more than mol / min ^-5 It is preferable that the amount be not more than mol (mol) / min. The first concentration, which is the concentration of the boron source supplied to the vapor phase growth region in the first step of forming the amorphous layer, is set to 1 × 10 ^-6 4 × 10 at more than mol / min ^-5 By setting the concentration to not more than mol (mol) / min, a flat amorphous layer having a maximum difference in height of surface irregularities of about 1 nm can be obtained. Here, the molar concentration is calculated assuming that the volume occupied by 1 mol of gas at a temperature of 25 ° C. and a pressure of 1 atm is 24.46 liters (unit: l). 4 × 10 ^-5 When a high concentration boron source is supplied at a rate exceeding mol / min, hemispherical irregularities are generated and it becomes difficult to obtain an amorphous layer having a flat surface. On the other hand, when the supply amount of the boron source is 1 × 10 ^-5 If the amount is less than mol / min, there is a problem that a sufficiently continuous amorphous layer cannot be stably formed.
[0012]
On the amorphous material containing boron and phosphorus, a boron phosphide crystal layer is vapor-phase grown by the above-mentioned vapor-phase growth means. For example, diborane (B ₂ H ₆ ) As a boron source and phosphine (PH ₃ ) Is vapor phase grown by hydride means using a phosphorus source. Temperature T for vapor-phase growth of boron phosphide crystal layer ₂ Is in the range of 750 ° C. or more and 1200 ° C. or less. At a low temperature of less than 750 ° C., a polycrystalline or amorphous boron phosphide layer is easily formed, so that it is difficult to reach a temperature suitable for obtaining a single crystal boron phosphide crystal layer. At high temperatures above 1200 ° C, B ₁₃ P ₂ This is not preferred because a multimeric boron phosphide is easily formed. Furthermore, in order to avoid the amorphous layer being thermally denatured, it is preferable that the boron phosphide crystal layer be grown within the above-mentioned temperature range, particularly at a growth temperature of the amorphous layer or lower. The means for subsequently forming the vapor phase growth of the boron phosphide crystal layer by using the same vapor phase growth apparatus as that for forming the amorphous layer is a method of obtaining the boron phosphide crystal layer simply and labor-saving. Can be made. After the vapor phase growth of the amorphous layer is completed, a phosphorus source is supplied to the vapor phase growth region for the purpose of preventing the volatilization and deviation of phosphorus from the amorphous phase, and the vapor phase growth of the boron phosphide crystal layer is performed. This is because the process can be shifted to the process.
[0013]
The boron phosphide crystal layer has a V / III ratio of 1.5 × 10 ² 1 x 10 ⁴ The vapor phase growth is performed in the following range. In order to obtain a monomeric boron phosphide (BP) crystal layer, the V / III ratio is 1 × 10 ⁴ Do not set the ratio higher than Further, the V / III ratio is set to 1.5 × 10 ² If the ratio is lower than the above, the situation becomes relatively rich in boron, which causes a disadvantage that a hemispherical growth hill results in a boron phosphide crystal layer lacking in flatness of a dense surface. The morphology of the surface of the boron film composed of a spherical boron crystal can be seen from a published publication (see J. Solid State Chem., 133 (1997), pp. 314 to 321).
[0014]
In addition to setting the V / III ratio in a range suitable for vapor-phase growth of the boron phosphide crystal layer, in the present invention, particularly, in the second step of vapor-phase growth of the boron phosphide crystal layer, The second concentration, which is the concentration of boron atoms supplied to the vapor phase growth region, is different from the first concentration, which is the concentration of boron atoms supplied in the first step of vapor phase growing the amorphous layer. , 1/30 or more and 1/5 or less. Specifically, 3.3 × 10 ^-8 8 × 10 at more than mol / min ^-6 Mol / min or less. By setting the supply amount of boron atoms per unit time to a second concentration lower than that in the case of the amorphous layer, the growth rate of the boron phosphide crystal layer is reduced, thereby avoiding the generation of voids and achieving a dense structure. In addition, it is for obtaining a continuous single crystal layer without a gap. The concentration of boron atoms supplied per unit time is sufficient if the flow rate of the boron source supplied per unit time to the vapor phase growth region is simply reduced.
[0015]
During the vapor phase growth of the boron phosphide crystal layer, doping for intentionally adding impurities can be performed. For example, an element belonging to Group IV of the periodic rule, such as silicon (Si), carbon (C), or tin (Sn), can be doped as an amphoteric impurity. Further, a group II element such as zinc (Zn) or beryllium (Be) can be doped as a p-type impurity. The boron phosphide crystal layer is changed to the vapor phase growth temperature T of the amorphous layer. ₁ The following temperature T ₂ The effect of suppressing vapor diffusion and permeation of the added impurity into other layers is obtained by performing the vapor phase growth. After vapor-growing the boron phosphide crystal layer, the impurity can also be added to the boron phosphide layer by means of ion implantation of impurities (ion implantation method). If the ion implantation method is used, not only impurities imparting conductivity, but also hydrogen ions (H) capable of electrically compensating a carrier can be used. ⁺ ; Protons). If the impurity ions are implanted only in a selected region of the boron phosphide crystal layer using the selective ion implantation method, the carrier concentration and the resistivity can be changed only in a specific region.
[0016]
On the other hand, as described above, the inside of the boron phosphide crystal layer grown at a suitable temperature, V / III ratio, and supply amount of the boron source per unit time contains boron vacancies or phosphorus vacancies in the first place. There is a large amount of donor or acceptor involved. Therefore, p-type or n-type conductivity can be obtained in an undoped state without intentionally adding impurities. Since the undoped conductive layer does not have to worry about inversion or lowering of the conductivity type of another layer due to diffusion of the doped impurity, it can be effectively used as, for example, a barrier (cladding) layer or the like constituting a light emitting element. Available.
[0017]
A group III nitride semiconductor layer such as gallium nitride (GaN) is vapor-phase grown on the boron phosphide crystal layer. Since the amorphous layer according to the present invention is vapor-phase grown as an underlayer, the boron phosphide crystal layer has excellent flat surface crystallinity. The high quality boron phosphide crystal layer has an effect of providing a group III nitride semiconductor layer having excellent crystallinity. The group III nitride semiconductor layer can be formed by a vapor phase growth method similarly to the above-mentioned amorphous layer and boron phosphide crystal layer. In particular, when the group III nitride semiconductor layer is grown using the same vapor phase growth means and vapor phase growth apparatus following the vapor phase growth of the amorphous layer and the boron phosphide crystal layer, the group III nitride An object semiconductor layer can be obtained. Temperature T at which group III nitride semiconductor layer is grown in vapor phase ₃ With the vapor phase growth temperature T of the boron phosphide crystal layer. ₂ In this case, a high-quality boron phosphide crystal layer can be grown in a vapor phase while suppressing thermal denaturation of the boron phosphide crystal layer as the underlayer. However, trimethylgallium ((CH ₃ ) ₃ Gallium (Ga) source such as Ga) or ammonia (NH) ₃ In order to stably form a film by thermally decomposing a nitrogen (N) source such as), the vapor phase growth temperature is at least 250 ° C. or higher. The V / III ratio when the group III nitride semiconductor layer is vapor-phase grown is set to be equal to or larger than the ratio when the boron phosphide crystal layer is vapor-phase grown. Approx. 1 × 10 ⁴ ~ 5 × 10 ⁴ It is preferable to
[0018]
By using the group III nitride semiconductor crystal layer having excellent crystallinity according to the present invention, a high performance group III nitride semiconductor device can be formed. For example, a group III nitride semiconductor layer grown in a vapor phase under the above temperature conditions is used as a barrier layer, and a light emitting layer having a single or multiple quantum well structure is provided on the barrier layer. Can be formed. By using the group III nitride semiconductor layer according to the present invention as a base layer, a junction interface between a barrier layer and a well layer forming a quantum well structure provided thereon can be made flat. Therefore, a substantially constant quantum level is expressed in each well layer, and a semiconductor light emitting device that emits light with excellent monochromaticity can be provided. Also, for example, a high-purity n-type gallium-indium nitride mixed crystal (Ga) grown in vapor phase on a high-resistance boron phosphide crystal layer _X In _1-X If the (N: 0 ≦ X ≦ 1) layer is used as a channel layer, a Schottky junction field effect transistor (MESFET) can be formed.
[0019]
【Example】
Hereinafter, an amorphous layer containing boron and phosphorus, a boron phosphide (BP) crystal layer, and a group III nitride semiconductor layer are sequentially formed on a silicon (Si) single crystal substrate using MOCVD vapor phase epitaxy. The content of the present invention will be specifically described by taking, as an example, a case where a light emitting diode is formed from the laminated structure.
[0020]
The structure of the laminated structure 1B for constituting the LED 1A is shown in a schematic sectional view of FIG. As the substrate 101, a p-type conductive Si single crystal having a (111) -crystal plane inclined by 2 ° with respect to the [110] crystal direction was used. After placing the Si single crystal substrate 101 on a high-purity graphite susceptor of a MOCVD vapor phase epitaxy apparatus, the temperature of the substrate 101 is reduced from room temperature to 1025 ° C. in a hydrogen atmosphere by a high frequency induction heating method. The temperature rose. Then, triethyl boron ((C ₂ H ₅ ) ₃ B) as a boron source and phosphine (PH ₃ The amorphous layer 102 containing boron and phosphorus was vapor-phase grown by a normal pressure (substantially atmospheric pressure) MOCVD method using) as a phosphorus source. The boron source is high-purity hydrogen gas (H ₂ ) And bubbling with triethyl boron ((C ₂ H ₅ ) ₃ The bubbling hydrogen gas accompanying the vapor of B) was mixed with a hydrogen carrier gas at a flow rate of 16 liters per minute and supplied to the vapor phase growth region. The supply amount of the boron source per unit time (= 1 minute) (first concentration which is the concentration of boron atoms supplied in the first step of the present invention) when the amorphous layer 102 is vapor-phase grown is , 2.0 × 10 ^-5 Mol / min (calculated assuming that the volume of one mole of gas was 24.46 liters). Also, the V / III ratio (= PH ₃ / (C ₂ H ₅ ) ₃ B) was set to 16. The layer thickness of the amorphous layer 102 was 20 nm.
[0021]
After forming the amorphous layer 102, a boron source ((C ₂ H ₅ ) ₃ The addition of the hydrogen gas for bubbling accompanied with the vapor of B) to the hydrogen carrier gas was temporarily stopped. After that, the temperature of the Si single crystal substrate 101 was lowered from 1025 ° C. to 850 ° C. in a mixed atmosphere of hydrogen and phosphine. Next, the supply of the boron source to the vapor phase growth region was started again, and an undoped p-type boron phosphide crystal layer 103 was vapor-phase grown on the amorphous layer 102 by the same MOCVD means as described above. . The supply amount of boron atoms per unit time (= 1 minute) supplied when growing the p-type boron phosphide crystal layer 103 (the second concentration which is the concentration of boron atoms supplied in the second step of the present invention). Concentration) is 2.2 × 10 ^-6 It was set to mol / min. This second concentration was calculated with a volume of one mole of gas of 24.46 liters. The boron phosphide crystal layer 103 was grown with the V / III ratio being 1008. The carrier concentration of the p-type boron phosphide crystal layer 103 at room temperature is about 1 × 10 ¹⁹ cm ^-3 And the layer thickness was about 100 nm.
[0022]
Subsequently, the supply of the boron source and the phosphorus source to the vapor phase growth region was stopped, and the temperature of the single crystal substrate 101 was reduced to 800 ° C. while only the hydrogen carrier gas was allowed to flow. Next, ammonia gas (NH ₃ ) To the vapor phase growth area. Thereafter, trimethylgallium ((CH) as a gallium (Ga) source was introduced into the vapor phase growth region in which the atmosphere was a mixture of hydrogen and ammonia. ₃ ) ₃ Ga) vapor was added. At the same time, trimethylindium ((CH ₃ ) ₃ In) vapor was added. Thus, the n-type gallium indium nitride (Ga) is formed on the p-type boron phosphide crystal layer 103. _0.90 In _0.10 N) A semiconductor layer 104 was deposited. n-type gallium indium nitride (Ga _0.90 In _0.10 N) The V / III ratio when laminating semiconductor layers is 1 × 10 ⁴ And The carrier concentration of the n-type gallium indium nitride layer 104 is about 6 × 10 ¹⁸ cm ^-3 And the layer thickness was about 30 nm.
[0023]
The supply of the gallium source and the indium source to the vapor growth region was stopped, and the vapor growth of the gallium indium nitride semiconductor layer 104 was completed. At the same time, the supply of ammonia gas to the vapor phase growth region was also stopped. Next, while the Si single crystal substrate 101 is kept at 800 ° C., the supply of the above-mentioned boron source and phosphorus source to the vapor-phase growth region is started again, and the n-type boron phosphide crystal layer 105 is vapor-phase-grown. Was. The supply amount of the boron source per unit time during the vapor phase growth of the n-type boron phosphide crystal layer 105 is the same as the second concentration when the p-type boron phosphide crystal layer 103 was formed, that is, 2.2 ×. 10 ^-6 Mol / min and the V / III ratio (= PH ₃ / (C ₂ H ₅ ) ₃ B) was also set to 1008. The carrier concentration of the undoped n-type boron phosphide crystal layer 105 is about 2 × 10 ¹⁹ cm ^-3 And the layer thickness was about 300 nm. The supply of both the boron source and the phosphorus source to the vapor phase growth region was stopped to terminate the growth of the n-type boron phosphide crystal layer 105.
[0024]
Since both the p-type boron phosphide crystal layer 103 and the n-type boron phosphide crystal layer 105 have a band gap of about 3 eV at room temperature, a clad for the light emitting layer composed of the gallium-indium nitride semiconductor layer 104 is formed. It could be used effectively as a layer. Thus, a double hetero (DH) having the p-type boron phosphide crystal layer 103 as a lower cladding layer, the n-type gallium indium nitride semiconductor layer 104 as a light emitting layer, and the n-type boron phosphide crystal layer 105 as an upper cladding layer. A laminated structure 1B provided with a light emitting portion having a joint structure was formed. Since the p-type boron phosphide crystal layer 103 was vapor-phase grown at a temperature equal to or lower than the growth temperature of the amorphous layer 102 in order to suppress thermal denaturation of the amorphous layer 102, the lower cladding having excellent flatness and continuity was obtained. Could be a layer. Further, since the n-type gallium-indium nitride semiconductor layer 104 is vapor-phase grown at a lower temperature than the p-type boron phosphide crystal layer 103, the surface of the p-type boron phosphide crystal layer 103 is flattened while suppressing thermal denaturation. Thus, a light emitting layer composed of a continuous film having excellent properties was formed. Further, the amorphous silicon layer 103 and the p-type boron phosphide crystal layer 103 and the gallium / indium nitride semiconductor layer 104 which are grown on the silicon single crystal substrate 101 via the amorphous layer 102 are amorphous. The density of misfit dislocations propagated from the bonding interface with the porous layer 102 is about 1 × 10 ³ cm ^-2 From 1 × 10 ⁴ cm ^-2 It was estimated.
[0025]
In the center of the n-type boron phosphide crystal layer 105, which is the outermost layer of the laminated structure 1B, Au.Ge/nickel (Ni) in which the side in contact with the layer 105 is made of a gold-germanium (Au.Ge) alloy ) / Au n-type ohmic electrode 106 having a three-layer structure was provided. The n-type ohmic electrode 106 also serving as a pedestal (pad) electrode for connection was a circular electrode having a diameter of about 120 μm. An aluminum (Al) electrode was disposed as a p-type ohmic electrode 107 on substantially the entire back surface of the p-type Si single crystal substrate 101. The thickness of the deposited Al film was about 2 μm. Thus, an LED 1A having a pn junction type DH structure was formed. When an operating current of 20 milliamperes (mA) was passed between the n-type ohmic electrode 106 and the p-type ohmic electrode 107 in the forward direction, the LED 1A emitted blue-violet light having a wavelength of about 440 nm. The luminance in a chip state measured using a general integrating sphere was 9 millicandela (mcd), and the LED 1A with high light emission intensity was provided. The forward current was set to 20 mA, reflecting that a flat junction interface was formed between the gallium indium nitride light emitting layer and the upper and lower clad layers composed of p-type and n-type boron phosphide crystal layers. The LED 1A having good rectification characteristics in which the forward voltage (Vf) at this time is about 3.1 V and the reverse voltage (Vr) at 5.5 μV or more when the reverse current is 10 μA is provided.
[0026]
【The invention's effect】
In the present invention, first, an amorphous layer containing boron and phosphorus having an action of relaxing lattice mismatch between a silicon single crystal and a boron phosphide crystal layer is vapor-phase grown on the surface of a silicon (Si) single crystal substrate. After that, the concentration of boron atoms supplied from the vapor phase growth region per unit time and the ratio of the supply concentration of the phosphorus source to the boron source (V / III ratio) are varied to vapor-grow the boron phosphide crystal layer. Further, since the group III nitride semiconductor layer is vapor-phase grown at a temperature at which the thermal denaturation of the boron phosphide crystal layer can be suppressed, a flat surface of the boron phosphide semiconductor layer with the thermal denaturation suppressed is formed on the boron phosphide semiconductor layer. In addition, the effect of growing a group III nitride semiconductor semiconductor layer having a low misfit dislocation density and a good crystal quality can be enhanced.
[0027]
Further, according to the present invention, for example, a pn junction structure having a flat junction interface can be formed by using a good quality group III nitride semiconductor layer having a small crystal defect density as described above, so that good rectification can be achieved. It is possible to provide a group III nitride semiconductor device such as a group III nitride semiconductor light emitting device with high luminance that can exhibit characteristics.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an LED according to an embodiment of the present invention.
[Explanation of symbols]
1A LED
1B laminated structure
101 Si single crystal substrate
102 Amorphous layer containing boron and phosphorus
103 p-type boron phosphide crystal layer
104n gallium indium nitride layer
105 n-type boron phosphide crystal layer
106 n-type ohmic electrode
107 p-type ohmic electrode

Claims (8)

A phosphorus source with respect to a concentration of a boron source supplied per unit time to a vapor phase growth region at a temperature T ₁ (unit: ° C.) (250 ° C. ≦ T ₁ ≦ 1200 ° C.) on the surface of a silicon (Si) single crystal substrate. Is defined as a first ratio of not less than 0.2 and not more than 40, and the concentration of boron atoms supplied from a boron source within a unit time is defined as a first concentration. A first step of vapor-phase growing an amorphous layer containing boron (B) and phosphorus (P);
On the amorphous layer, at a temperature T ₂ (unit: ° C.) (provided that 750 ° C. ≦ T ₂ ≦ 1200 ° C.), the V / III ratio is set to a second ratio equal to or more than the first ratio, and within a unit time. A second step in which the concentration of boron atoms supplied from the boron source is set to a second concentration equal to or lower than the first concentration, and a boron phosphide (BP) crystal layer is vapor-phase grown;
A group III nitride semiconductor layer is vapor-phase grown on the boron phosphide crystal layer at a temperature T ₃ (unit: ° C.) of T ₂ or less and 250 ° C. or more (250 ° C. ≦ T ₃ ≦ T ₂ ). A third step;
A method for vapor-phase growing a group III nitride semiconductor layer, comprising: 2. The method according to claim 1, wherein the thickness of the amorphous layer is 1 nm or more and 50 nm or less. 3. The method according to claim 1, wherein, in the second step, the boron phosphide crystal layer is vapor-phase grown with a V / III ratio in a range from 1.5 × 10 ² to 1 × 10 ^4. The method for vapor-phase growth of a group III nitride semiconductor layer according to the above. And wherein the boron phosphide (BP) crystal layer temperature T ₂ which is grown in vapor phase in a second step, the amorphous layer and the temperature T ₁ of a temperature below the vapor phase growth in the first step The method for vapor-phase growing a group III nitride semiconductor layer according to claim 1. The second concentration, which is the concentration of boron atoms supplied in the second step, is 1/30 or more of the first concentration, which is the concentration of boron atoms supplied in the first step. 5. The method for vapor-phase growth of a group III nitride semiconductor layer according to claim 1, wherein the thickness is not more than / 5. The first concentration, which is the concentration of boron atoms supplied in the first step, is set to 1 × 10 ⁻⁶ mol (mol) / min or more and 4 × 10 ⁻⁵ mol / min or less; 6. The method according to claim 5, wherein the second concentration, which is the concentration of the boron atom supplied in the step (a), is not less than 3.3 × 10 ⁻⁸ mol / min and not more than 8 × 10 ⁻⁶ mol / min. A vapor phase growth method for a group III nitride semiconductor layer. 7. The group III nitride according to claim 1, wherein, in the third step, the group III nitride semiconductor layer is vapor-phase grown with a V / III ratio of 1 × 10 ^{4 to} 5 × 10 ^4. For growing a semiconductor layer. The method for vapor-phase growing a group III nitride semiconductor layer according to any one of claims 1 to 7, wherein the surface of the silicon (Si) single crystal substrate contains boron (B) and phosphorus (P). A group III nitride semiconductor device manufactured by sequentially vapor-phase growing a crystalline layer, a boron phosphide crystal layer, and a group III nitride semiconductor layer.

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