JP2004039827A - Method for vapor phase growing boron phosphide layer, boron phosphide semiconductor element, and light emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a boron phosphide layer of a single crystal having little crystal defect density cannot be stably formed due to a large lattice mismatching degree of an Si single crystal substrate and the boron phosphide layer. <P>SOLUTION: A method for vapor phase growing the boron phosphide layer includes steps of vapor phase growing a first boron phosphide layer by setting a ratio of the concentration of a phosphorus source to that of a boron source supplied to a vapor phase growing region is set in a range of 0.5 to 50, subsequently increasing the ratio to a range of 500 to 6,000 within 10 s, and vapor growing a second boron phosphide layer on the first boron phosphide layer. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vapor growth method for forming a boron phosphide layer having excellent crystallinity on a surface of a silicon single crystal substrate by relaxing lattice mismatch with the silicon single crystal, and a vapor growth method thereof. The present invention relates to a boron phosphide-based semiconductor having a boron phosphide layer formed by using the method described above.
[0002]
[Prior art]
Conventionally, boron phosphide (BP) layers containing boron (B) and phosphorus (P) as constituent elements have been used as functional layers for forming various semiconductor elements. For example, an n-type boron phosphide layer of a monomer is used as an n-type emitter layer of an npn-type hetero bipolar transistor (HBT) (J. Electrochem. Soc., 125 (4) (1978), 633-637). In a blue laser diode (LD), it is used as a contact layer for forming an ohmic electrode having a low contact resistance (see Japanese Patent Application Laid-Open No. 10-242567). Further, it is used as a buffer layer for constituting a light emitting diode (LED) that emits light of a short wavelength such as near ultraviolet or blue (see US Pat. No. 6,069,021).
[0003]
Means for vapor-phase growth of a boron phosphide layer include conventionally known boron trichloride (BCl₃) And phosphorus trichloride (PCl₃) As a starting material (see “Journal of the Japan Society for Crystal Growth”, Vol. 24, No. 2 (1997), p. 150), borane (BH)₃) Or diborane (B₂H₆) And phosphine (PH₃) (See J. Crystal @ Growth, 24/25 (1974), pp. 193 to 196) and molecular beam epitaxy (J. Solid @ Chem., 133 (1997), 269-). 272) and metal organic chemical vapor deposition (MOCVD) using organoboron compounds and hydrogen compounds of phosphorus as raw materials (Inst. Phys. Conf. Ser., No. 129 (IOP Publishing Ltd. (UK)). 1993), pp. 157-162).
[0004]
Conventionally, a substrate for vapor-phase growth of a boron phosphide layer includes a silicon (Si) single crystal (silicon) ((1) J. Electrochem. Soc., 125 (1978), and (2) And US Pat. No. 6,069,021). However, the lattice constant of the Si single crystal is 5.431%, and the lattice constant of zinc-blende BP is 4.538% (Takamoto Teramoto, “Introduction to Semiconductor Devices” (March 30, 1995, ) Baifukan first edition), page 28). Therefore, the degree of lattice mismatch is as large as about 16.5% (Katsubo Shono, "Semiconductor Technology (1)", June 25, 1992, published by The University of Tokyo Press, 9th pp. 97-98). reference). Further, the temperature range in which a single crystal boron phosphide layer can be obtained using a silicon single crystal as a substrate by a halogen vapor deposition method is limited to an extremely narrow range of 1020 ° C. to 1070 ° C. (“Applied physics”). 45 No. 9 (1976), pp. 891-896).
[0005]
[Problems to be solved by the invention]
In the present invention, when a boron phosphide layer is deposited on the surface of a Si single crystal substrate by vapor phase growth means, the temperature at which the single crystal layer is obtained is limited to a narrow range in the first place, A problem that a single crystal boron phosphide layer having a low crystal defect density cannot be stably formed due to a large degree of lattice mismatch between the crystal substrate and the boron phosphide layer is solved.
[0006]
[Means for Solving the Problems]
That is, the present invention
(1) Both a boron source containing a boron (B) atom and a phosphorus source containing a phosphorus (P) atom are supplied in parallel to a vapor phase growth region, and boron and a boron source are deposited on a silicon (Si) single crystal substrate. In a method for vapor-phase growing a boron phosphide (BP) layer containing phosphorus, the ratio of the concentration of the phosphorus source to the concentration of the boron source supplied to the vapor-phase growth region is set to 0.1. A first ratio (R₁After the first boron phosphide layer is vapor-phase-grown as (1), the ratio of the concentration of the phosphorus source to the concentration of the boron source is continuously adjusted within 10 seconds.₁To a second ratio (R₂), And vapor-phase growing a second boron phosphide layer on the first boron phosphide layer.
(2) The vapor phase of the boron phosphide layer according to (1), wherein the first boron phosphide layer and the second boron phosphide layer are vapor-phase grown using the same boron source. Growth method.
(3) The boron phosphide according to the above (1) or (2), wherein the first boron phosphide layer and the second boron phosphide layer are grown in vapor phase using the same phosphorus source. The vapor phase growth method of the layer.
(4) The above-mentioned (1) to (3), wherein the first boron phosphide layer and the second boron phosphide layer are vapor-phase grown by setting the temperature of the Si single crystal substrate to 750 ° C. or more and 1200 ° C. or less. ).
(5) The first boron phosphide layer is subjected to vapor phase growth by metal organic chemical vapor deposition (MOCVD) at a temperature of the silicon crystal substrate of 1000 ° C. or more and 1200 ° C. or less. The method for vapor-phase growing a boron phosphide layer according to any one of 1) to (4).
(6) The vapor phase growth method for a boron phosphide layer according to any one of the above (1) to (5), wherein the first boron phosphide layer is made of amorphous.
(7) The vapor phase growth method for a boron phosphide layer according to the above (1) to (6), wherein the first boron phosphide layer has a thickness of 2 to 50 nm.
(8) The vapor phase growth method for a boron phosphide layer according to any one of the above (1) to (7), wherein the second boron phosphide layer is made of a single crystal.
It is.
[0007]
Also, the present invention
(9) A boron phosphide-based semiconductor device comprising a boron phosphide layer grown by the vapor phase growth method according to any one of (1) to (8).
(10) An LED comprising the boron phosphide-based semiconductor device according to (9).
It is.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In this specification, a vapor phase growth region is a region in a vapor phase growth means in which a reaction for depositing a boron phosphide layer on the surface of a Si single crystal substrate is performed. A feature of the vapor phase growth method of the boron phosphide layer according to the present invention is that the first boron phosphide layer and the second boron phosphide layer grown at different concentration ratios of the boron source and the phosphorus source supplied to the vapor phase growth region are provided. It is to form a boron phosphide layer by laminating a boron phosphide layer.
[0009]
The concentration ratio of the phosphorus source to the boron source is a numerical value generally referred to as a V / III ratio, and is, for example, boron supplied to the vapor phase growth region in a unit time expressed in units of mol (mol) / minute. It is the ratio of the concentration of phosphorus atoms to the concentration of atoms. The concentration of boron atoms or phosphorus atoms is the atomic concentration of boron or phosphorus released when it is assumed that the boron source and the phosphorus source are completely thermally decomposed. In a boron or phosphorus source containing one boron or phosphorus atom, the V / III ratio can be represented by the ratio of the flow rates of both sources supplied to the vapor phase growth region. For example, when a boron phosphide layer is grown by MOCVD, triethyl boron ((C₂H₅)₃B) 0.03 cc / min, phosphine (PH₃) Is supplied at 230 cc / min, the V / III ratio is about 7.7 × 10³Is calculated.
[0010]
The first boron phosphide layer is used as a base layer for vapor-phase growing the second boron phosphide layer. In particular, when a substrate is made of Si single crystal having a large degree of lattice mismatch with boron phosphide, the first boron phosphide layer provided to be bonded to the substrate surface has a lattice mismatch between the substrate and the boron phosphide layer. And the effect of vapor-phase growing the second boron phosphide layer having excellent crystallinity is exerted. The effect of alleviating the lattice mismatch caused by the first boron phosphide layer is more effectively exhibited when the first boron phosphide layer is made of amorphous. In order to obtain the first boron phosphide layer made of amorphous, the V / III ratio in the vapor phase growth of the boron phosphide layer is set to a first ratio (R₁) Is preferable. When the V / III ratio is set to 0.5 or more, the formation of hemispherical boron grains can be avoided, and a first amorphous boron phosphide layer having a flat surface can be stably obtained. On the other hand, when the V / III ratio exceeds 50, there is a disadvantage that a polycrystalline layer in which fine single crystal grains are scattered in an amorphous body is likely to be formed. The thickness of the amorphous boron phosphide layer is preferably 2 to 50 nm, and more preferably 10 to 30 nm. When the temperature of the crystal substrate is kept constant, for example, the thickness of the amorphous first boron phosphide layer can be controlled by adjusting the supply time of the boron source to the vapor phase growth region.
[0011]
The amorphous first boron phosphide layer is preferably grown in a vapor phase by setting the temperature of the crystal substrate to 750 ° C. to 1200 ° C. At a high temperature exceeding 1200 ° C., B is not the monomeric boron phosphide,₁₃P₂And the like. This is not preferred because a polycrystalline layer composed of multimeric boron phosphide crystals (see J. Am. Ceramic @ Soc., 47 (1) (1964), pp. 44-46) is easily formed. The first V / III ratio (R₁) Is preferably set to a larger value as the vapor phase growth temperature of the first boron phosphide layer is higher.
[0012]
In particular, the source of boron is triethyl boron ((C₂H₅)₃B) and the phosphorus source is phosphine (PH₃), When the temperature of the Si single crystal substrate is set to 1000 ° C. to 1200 ° C. by the metalorganic chemical vapor deposition (MOCVD) method, the boron phosphide layer is vapor-phase grown. An amorphous first boron phosphide layer containing a large amount can be formed. The amorphous boron phosphide layer containing a large amount of boron in a stoichiometric equivalent absorbs misfit dislocations and the like generated due to lattice mismatch between the Si single crystal and the second boron phosphide layer. Thus, a remarkable effect can be exerted to provide a second boron phosphide layer having excellent crystallinity.
[0013]
On the first amorphous boron phosphide layer, a second boron phosphide layer made of a single crystal is grown. The V / III ratio for providing the single-crystal second boron phosphide layer is a second ratio (R) in the range of 500 to 6000.₂) Is preferable. The second ratio (R₂) Is preferably set to a larger value as the vapor phase growth temperature of the second boron phosphide layer is higher. But R₂Is 10⁴If the ratio is too high, a problem arises in that a second boron phosphide layer having excellent surface flatness cannot be stably obtained due to the generation of phosphorus-related projections. Also R₂Is less than 500, it is inconvenient to stably obtain a single crystal boron phosphide layer. The supply amounts of the boron source and the phosphorus source to the vapor phase growth region can be precisely controlled by, for example, a mass flow meter (MFC).
[0014]
As with the first boron phosphide layer, the second boron phosphide layer is also preferably grown in a vapor phase with the temperature of the crystal substrate at 750 ° C. or more and 1200 ° C. or less. At high temperatures above 1200 ° C, B₁₃P₂This is inconvenient since a polycrystalline layer composed of a multimeric boron phosphide crystal (see J. Am. Ceramic Soc., Supra) is easily obtained.
[0015]
In continuously growing the first boron phosphide layer and the second boron phosphide layer, the V / III ratio is set to R₁To R₂When the second boron phosphide layer having a uniform surface flatness and orientation is vapor-phase grown, the effect is rapidly increased. This is because, after the vapor phase growth of the first boron phosphide layer is completed, the formation of a polycrystalline layer in the middle of the two layers can be avoided when the second boron phosphide layer is continuously vapor-phase grown. . V / III ratio is R₁To R₂In order to increase the V / III ratio, for example, the supply amount of the phosphorus source is increased stepwise with time while the supply amount of the boron source to the vapor phase growth region is kept constant. A technique can be exemplified. For example, (C₂H₅)₃While keeping the supply amount of B constant,₃Is increased stepwise to increase the V / III ratio over time. Further, in a method of increasing the supply amounts of the boron source and the phosphorus source linearly, stepwise, or in a curve at different rates as the film formation time elapses, the supply amount of the boron source is increased more than the rate of increase. The V / III ratio can also be increased over time by increasing the supply of the phosphorus source at a specific rate.
[0016]
In any of the above techniques for increasing the V / III ratio over time, the V / III ratio must be set to R in order to avoid polycrystal formation.₁Within 10 seconds from R₂Need to be increased. For example, R with 0.5₁R from 3000₂Increase in 5 seconds. The rate of increase of the V / III ratio in this case is about 600 per second. In addition, R where the V / III ratio is 50₁From 1 to 6000 in 1 second₂To increase. In this case, the increase rate of the V / III ratio is 5950 / sec. R₁To R₂The method of increasing the thickness redundantly for more than 10 seconds not only changes the quality of the amorphous first boron phosphide layer kept at a high temperature, but also causes the orientation in the first boron phosphide layer to be changed. This is inconvenient because it promotes formation of a single crystal layer or a polycrystalline layer lacking uniformity. As the V / III ratio is increased in a shorter time, the effect of avoiding the formation of a polycrystalline layer can be improved. In addition, the V / III ratio is R₂By rapidly increasing the thickness, a boron phosphide layer having a uniform orientation can be vapor-phase grown. The crystal structures of the first boron phosphide layer and the second boron phosphide layer, and the existence of the polycrystalline layer in the middle of both layers are determined by crystal analysis means such as general X-ray diffraction or electron diffraction. You can investigate using.
[0017]
V / III ratio is R₁To R₂The means for vapor-phase growing the second boron phosphide layer using the same boron source as that used for vapor-phase growth of the first boron phosphide layer is a simple and labor-saving method. This is a convenient way to obtain a second boron phosphide layer. If the boron source is the same, the V / III ratio can be increased only by a simple operation of increasing the supply amount of the phosphorus source to the vapor phase growth region, and the V / III ratio can be increased following the vapor phase growth of the first boron phosphide layer. This is convenient because the second boron phosphide layer can be continuously grown in vapor phase. Also, R₁To R₂In increasing the V / III ratio, the means for vapor-phase growing the second boron phosphide layer using the same phosphorus source used for vapor-phase growth of the first boron phosphide layer is as follows. This is a simple and labor-saving method for obtaining the second boron phosphide layer. If the phosphorus source is the same, the V / III ratio can be increased only by a simple operation of reducing the supply amount of the boron source to the vapor phase growth region, and the V / III ratio can be increased following the vapor phase growth of the first boron phosphide layer. This is convenient because the second boron phosphide layer can be continuously grown in vapor phase. The means for vapor-phase growing the first boron phosphide layer and the second boron phosphide layer with both the boron source and the phosphorus source being the same means only adjusting the supply amounts to both vapor-phase growth regions. This is particularly convenient because phase growth can be continued.
[0018]
If the first boron phosphide layer and the second boron phosphide layer are vapor-phase grown by the same means, it is a good idea to easily obtain the boron phosphide layer. In particular, according to the MOCVD method using an organic boron compound which thermally decomposes at a relatively low temperature as a boron source, it is suitable for obtaining a first boron phosphide layer which is preferably made of amorphous. Become. For example, if the boron source is triethyl boron ((C₂H₅)₃The MOCVD method B) is convenient because the amorphous first boron phosphide layer can be easily vapor-phase grown at a relatively low temperature depending on the triethylboron easy decomposability. Either normal pressure (substantially atmospheric pressure) or reduced pressure MOCVD means can be used for vapor phase growth of the boron phosphide layer. In the low-pressure MOCVD method, the pressure during the vapor phase growth is set to 0.1 atm or more in order to suppress excessive volatilization of phosphorus from the first boron phosphide layer and the second boron phosphide layer. Is desirable.
[0019]
According to the vapor phase growth method of the present invention, the second boron phosphide layer made of a single crystal and having a low crystal defect density and excellent surface flatness can be vapor phase grown over a wide range of temperatures. Therefore, if such a boron phosphide layer is used, for example, a pn junction structure having a flat junction interface can be stably formed. The vapor phase growth means of the present invention is not limited to the monomeric boron phosphide, but includes boron and phosphorus as constituent elements._αAl_βGa_γIn_{1- α − β − γ}P_{1- δ}As_δ(0 <α ≦ 1, 0 ≦ β <1, 0 ≦ γ <1, 0 <α + β + γ ≦ 1, 0 ≦ δ <1), for example, B_αAl_βGa_γIn_{1- α − β − γ}P_{1- δ}N_δ(0 <α ≦ 1, 0 ≦ β <1, 0 ≦ γ <1, 0 <α + β + γ ≦ 1, 0 ≦ δ <1) and the like can also be applied to the case of vapor phase growth on a Si single crystal substrate. In particular, boron phosphide / gallium (B) which increases the mixed crystal ratio of boron phosphide_αGa_γP: 0 <α ≦ 1, 0 ≦ γ <1), boron nitrided phosphide (BP_{1- δ}N_δ: 0 ≦ δ <1).
[0020]
[Action]
In a structure in which a first boron phosphide layer and a second boron phosphide layer are successively laminated on a Si single crystal substrate, the first boron phosphide layer made of amorphous is Has the effect of relaxing the lattice mismatch with the boron phosphide layer to provide a second boron phosphide layer made of a single crystal having a low defect density and a flat surface.
[0021]
【Example】
(First embodiment)
The content of the present invention will be specifically described by taking as an example a case where a monomeric boron phosphide layer is vapor-phase grown on a Si single crystal substrate by MOCVD. FIG. 1 schematically shows a schematic configuration of the MOCVD apparatus used in the first embodiment.
[0022]
As a preparation for vapor-phase growth of the first amorphous boron phosphide layer, a p-type Si single crystal substrate 101 having a (111) -Si crystal surface as a surface to which boron (B) is added is prepared. Was placed horizontally on a susceptor 12 made of high-purity graphite. After the mounting table was inserted into the load lock chamber 13 attached to the MOCVD vapor phase growth furnace 10 made of a high-purity quartz prism, the inside of the chamber 13 was replaced with nitrogen gas. Thereafter, the mounting table 12 on which the Si single crystal substrate 101 was mounted was transported to the vapor growth region 11 while flowing high-purity nitrogen gas at a rate of about 8 liters per minute into the MOCVD vapor growth reactor 10. After the transfer was completed, the supply of the nitrogen gas was stopped, and instead, a high-purity hydrogen gas was flowed at a flow rate of 16 liters per minute into the vapor phase growth region 11 as a carrier gas. Thereafter, the temperature of the substrate 101 was increased to 1025 ° C. in a hydrogen atmosphere by an induction heating method using a high-frequency coil 14 arranged around the outside of the vapor phase growth region 11.
[0023]
Next, on a Si single crystal substrate 101, triethyl boron ((C₂H₅)₃B) and phosphine (PH₃) Were supplied to the vapor phase growth region 10 to stack the first boron phosphide layer 102 made of amorphous. Triethyl boron was supplied by bubbling with hydrogen gas and adding hydrogen gas for bubbling accompanied by vapor of triethyl boron to the hydrogen carrier gas. The flow rate of hydrogen for foaming was adjusted to 45 cc / min. The flow rate of phosphine (concentration: 100%) was set at 48 cc / min. The V / III ratio when growing the first boron phosphide layer 102 (the first ratio R₁) Is 16. Hydrogen gas for blowing and phosphine accompanied by triethylboron are continuously added to the hydrogen carrier gas for 1.5 minutes, so that boron atoms having a layer thickness of about 10 nm are made richer than phosphorus atoms. Was grown.
[0024]
Next, the temperature of the Si single crystal substrate 101 was maintained at 1025 ° C., and the supply amount of the same boron source 16 to the vapor phase growth region 11 was 1.34 × 10 4^-4While maintaining the mol / min, the supply amount of the same phosphorus source 15 as described above was increased from 48 cc / min to 3000 cc / min in 1 second. That is, the V / III ratio is changed to the first ratio (= R₁) To the second ratio (= R₂) To 1000 in 5 seconds. Under these supply conditions, a boron source and a phosphorus source are continuously supplied to the vapor phase growth region 11 for 5 minutes, and a second boron phosphide made of an undoped p-type single crystal having a layer thickness of 450 nm is used. Layer 103 was vapor grown on first boron phosphide layer 102. After stopping the addition of the boron source 15 to the vapor phase growth region 11 and terminating the vapor phase growth of the second boron phosphide 103, the temperature of the Si single crystal substrate 101 was cooled to a temperature near room temperature. .
[0025]
After cooling, the Si single crystal substrate 101 on which the first boron phosphide layer 102 and the second boron phosphide layer 103 are stacked is taken out from the MOCVD vapor deposition reactor 10 and the first and second boron phosphide layers 102 , 103 were observed by an electron diffraction method. The first boron phosphide layer 102 was shown to be an amorphous layer because it provided a halo diffraction pattern without distinct diffraction spots. The second boron phosphide layer 103 was found to be a single crystal boron phosphide layer having a (111) plane from a spot pattern including a (220) diffraction point. According to cross-sectional TEM observation using a transmission electron microscope (TEM), a single-crystal second boron phosphide layer 103 grown by vapor phase using the first amorphous boron phosphide layer 102 as an underlayer. Almost no propagation of misfit dislocations into the inside was observed. No polycrystalline layer was found between the first boron phosphide layer 102 and the second boron phosphide layer 103. The maximum height difference of the irregularities on the surface of the second boron phosphide layer 103 measured using an atomic force microscope (AFM) was about 4 nm, and a surface excellent in flatness was obtained.
[0026]
(Second embodiment)
The content of the present invention will be specifically described by taking, as an example, a case where a boron phosphide-based LED is formed from the laminated structure 1B including the first boron phosphide layer and the second boron phosphide layer according to the present invention. I do.
[0027]
FIG. 2 is a schematic plan view of an LED 1A according to the second embodiment. FIG. 3 schematically shows a cross-sectional structure of the LED 1A along the broken line X-X 'in FIG. In FIG. 3, the same components as those described in the first embodiment are denoted by the same reference numerals.
[0028]
A laminated structure 1B according to the present invention includes a p-type Si single crystal substrate 101 having a surface that is 2 ° off from a (111) plane to which boron is added, and an amorphous structure formed sequentially on the substrate 101. A first boron phosphide layer 102, a second boron phosphide layer 103 made of undoped p-type single crystal, a light emitting layer 104 provided on the second boron phosphide layer 103, and an n-type phosphorus And a boron oxide layer 106. The first amorphous boron phosphide layer 102 is made of triethyl boron ((C₂H₅)₃B) as a boron source and phosphine (PH₃) Was formed by a normal pressure (substantially atmospheric pressure) MOCVD method using a phosphorus source. The first boron phosphide layer 102 has a growth temperature of 850 ° C. and a supply rate of a boron source (triethylboron) to the vapor phase growth region of 1.34 × 10 3 / min.^-4V / III ratio when growing the first boron phosphide layer 102, that is, the first ratio R₁Was set to 1 and grown. The thickness of the first boron phosphide layer 102 was set to about 20 nm.
[0029]
After the vapor phase growth of the first boron phosphide layer 102 made of amorphous is completed, the flow rate of the phosphorus source (phosphine) is increased every time while the supply amount of the boron source to the vapor phase growth region is maintained at the above value. It increased from 3 cc per minute to 1500 cc per minute in 3 seconds. Thus, the same boron source (triethyl boron) and phosphorus source (phosphine) as the raw materials used for growing the first boron phosphide layer 102 are used, and the second boron phosphide layer 103 is grown. V / III ratio, ie, the second ratio R₂Was set to 500, and vapor phase growth of the second boron phosphide layer 103 was started. The second boron phosphide layer 103 was vapor-phase grown at 850 ° C. by the normal pressure MOCVD method. The carrier concentration of the undoped p-type second boron phosphide layer 103 is about 8 × 10¹⁸cm^-3The layer thickness was set to about 300 nm.
[0030]
Next, while maintaining the temperature of the Si single crystal substrate 101 at 850 ° C., an n-type gallium-indium nitride mixed crystal (Ga) is formed on the single crystal second boron phosphide layer 103._XIn_1-XThe light-emitting layer 104 composed of an N) layer was provided by bonding. Ga forming the light emitting layer 104_XIn_1-XThe N layer is made of trimethylgallium ((CH₃)₃Ga) / trimethylindium ((CH₃)₃In) / Ammonia (NH)₃) / H₂It was formed using a normal pressure MOCVD method using a reaction system. Hexagonal wurtzite crystal type Ga_XIn_1-XThe indium composition ratio of N (= 1−X) is determined by the distance between the {111} -boron phosphide crystal plane perpendicular to the {111} -boron phosphide plane forming the surface of the second boron phosphide layer 103 ( {3.21}), 10% (= 0.10) so that the lattice constant of the a-axis matches.
[0031]
After the formation of the light emitting layer 104 is completed, while maintaining the temperature of the Si single crystal substrate 101 at 850 ° C., the light emitting layer 104 is formed on the light emitting layer 104 by a normal pressure MOCVD method using triethyl boron as a boron source and phosphine as a phosphorus source. An n-type boron phosphide layer 105 was laminated. The carrier concentration of the n-type boron phosphide layer 105 is about 7 × 10¹⁸cm^-3And the layer thickness was about 500 nm. Although the p-type second boron phosphide layer 103 and the n-type boron phosphide layer 105 have opposite conductivity types, each has a band gap of about 3 electron volts (unit: eV) at room temperature. ), It could be effectively used as a barrier (cladding) layer for the light emitting layer 104. Thus, a laminated structure 1B having a pn junction type double heterojunction light emitting portion composed of the p-type second boron phosphide layer 103, the n-type light emitting layer 104, and the n-type boron phosphide layer 105 is provided. Got.
[0032]
In the center of the n-type boron phosphide layer 105 which forms the surface layer of the multilayer structure 1B, Au.Ge/nickel (Ni) / a gold / germanium (Au.Ge) alloy film is used on the side in contact with the layer 105. An n-type ohmic electrode 106 having a three-layer Au structure was provided. The n-type ohmic electrode 106 also serving as a pedestal electrode for connection was a circular electrode having a diameter of about 130 μm. In addition, a p-type ohmic electrode 107 made of aluminum (Al) is arranged on substantially the entire back surface of the p-type Si single crystal substrate 101. The thickness of the deposited Al film was about 2.5 μm. Thus, an LED 1A having a pn junction type DH structure was formed.
[0033]
An operating current of 20 milliamperes (mA) was passed through the LED 1A in the forward direction through the n-type ohmic electrode 106 and the p-type ohmic electrode 107 to emit 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). Further, since the n-type light emitting layer 104 and the second boron phosphide layer 103 having a flat surface form a light emitting portion of a pn junction type, the bonding interface becomes flat, and accordingly, a forward voltage (however, (When the forward current was 20 mA), which was a low value of about 3.1 V. In addition, local breakdown voltage failure (local breakdown) caused by dislocations is hardly observed, and misfit dislocations to the light emitting portion due to the effect of the amorphous first boron phosphide layer 102 are generated. It was shown that propagation was suppressed. As a result, a high-luminance boron phosphide-based LED having a good rectifying characteristic resulting from a good pn junction structure and having a reverse voltage (provided that the reverse current is 10 μA) of 5 V or more is provided. It became a thing.
[0034]
【The invention's effect】
In the present invention, the ratio of the concentration of the phosphorus source to the concentration of the boron source supplied to the vapor-phase growth region is set to a relatively low value of 0.5 to 50, and the first boron phosphide layer of the amorphous state is formed. Is vapor-phase-grown, and then a single-crystal second boron phosphide layer is vapor-phase-grown on the layer at a higher ratio of 500 to 6000. The effect of forming a single crystal layer of boron phosphide with excellent surface flatness and low crystal defect density and excellent crystallinity in a wide temperature range, in combination with the action of alleviating the lattice mismatch caused by the boron layer. is there.
[0035]
Further, according to the present invention, the first boron phosphide layer and the second boron phosphide layer are formed using the same boron source, the same phosphorus source, or the same boron source and the same phosphorus source. Thus, the single crystal boron phosphide layer can be easily formed continuously on the amorphous boron phosphide layer.
[0036]
Further, according to the present invention, the temperature of the Si single crystal substrate is set at 1000 ° C. or more and 1200 ° C. or less, and the first boron phosphide layer is vapor-phase grown by the MOCVD method. This is effective in simply forming the first stoichiometric amorphous boron phosphide layer.
[0037]
Further, according to the present invention, the second phosphide composed of a single crystal having a low crystal defect density and having excellent surface flatness, which is vapor-phase grown using the first amorphous boron phosphide layer as an underlayer. Since the boron phosphide-based semiconductor element is formed by using the boron layer, for example, a high-quality pn junction structure having a flat junction interface can be formed, and high-luminance boron phosphide having excellent rectification characteristics and breakdown voltage characteristics can be formed. A system light emitting diode can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a schematic configuration of a MOCVD apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic plan view of an LED according to a second embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view of the LED shown in FIG. 2 along the dashed line X-X '.
[Explanation of symbols]
1A LED
1B laminated structure
10 MOCVD vapor phase growth furnace
11 vapor phase growth region
12 mounting table
13 Road lock room
14 high frequency coil
15 phosphorus source
16% boron source
101 Si single crystal substrate
102 first boron phosphide layer
103—second boron phosphide layer
104 luminescent layer
105 n-type boron phosphide layer
106 n-type ohmic electrode
107 p-type ohmic electrode

Claims (10)

By supplying both a boron source containing a boron (B) atom and a phosphorus source containing a phosphorus (P) atom to the vapor phase growth region, boron and phosphorus are deposited on a silicon (Si) single crystal substrate. In a method for vapor-phase growing a boron phosphide (BP) layer containing vapor-phase, the ratio of the concentration of the phosphorus source to the concentration of the boron source supplied to the vapor-phase growth region is 0.5 to 50. After the first boron phosphide layer is vapor-phase-grown as a _first ratio (R ₁ ) in the range, the ratio of the concentration of the phosphorus source to the concentration of the boron source is changed from the above R ₁ within 10 seconds. Increasing the second ratio (R ₂ ) in the range of 500 to 6000, and vapor-growing the second boron phosphide layer on the first boron phosphide layer; Phase growth method. 2. The method according to claim 1, wherein the first boron phosphide layer and the second boron phosphide layer are vapor-phase grown using the same boron source. 3. The vapor phase growth method for a boron phosphide layer according to claim 1, wherein the first boron phosphide layer and the second boron phosphide layer are vapor-phase grown using the same phosphorus source. . 4. The method according to claim 1, wherein the first boron phosphide layer and the second boron phosphide layer are vapor-phase grown by setting the temperature of the Si single crystal substrate to 750 ° C. or more and 1200 ° C. or less. 3. The method for vapor-phase growth of a boron phosphide layer according to item 1. 5. The method according to claim 1, wherein the first boron phosphide layer is grown in a vapor phase by metal organic chemical vapor deposition (MOCVD) at a temperature of the silicon crystal substrate of 1000.degree. C. to 1200.degree. The method for vapor-phase growth of a boron phosphide layer according to any one of the above. 6. The method according to claim 1, wherein the first boron phosphide layer is made of amorphous. 7. The vapor phase growth method for a boron phosphide layer according to claim 1, wherein the first boron phosphide layer has a thickness of 2 to 50 nm. 8. The method for vapor-phase growth of a boron phosphide layer according to claim 1, wherein the second boron phosphide layer is made of a single crystal. A boron phosphide-based semiconductor device comprising a boron phosphide layer grown by the vapor phase growth method according to claim 1. An LED comprising the boron phosphide-based semiconductor device according to claim 9.

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