JPH06196755A - Indium gallium nitride semiconductor and method of growing the same - Google Patents

Abstract

PURPOSE:To improve a crystallizability and a quality of an indium gallium nitride (InGaN) semiconductor and obtain the practical InGaN, by doping Si or Ge into the InGaN semiconductor represented in a specific general expression and growing it. CONSTITUTION:In a method of growing an indium gallium nitride compound semiconductor by a metal organic chemical vapor deposition (MOCVD) method, a gas of a gallium source, a gas of an indium source, a gas of a nitrogen source and a gas of a silicon source or a germanium source are used as a material gas, and further a carrier gas of the material gas is used as a nitrogen, and the indium gallium nitride semiconductor represented in a general expression InxGa1-NN (where 0<x (0.5) into which Si or Ge is doped is grown on a gallium nitride layer at a growth temperature of higher than 600 deg.C. A crystallizability and a quality of the semiconductor can be further improved and the practical InGaN is obtained, and a semiconductor material stacked in a blue luminescent device can be formed in a double hetero structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indium gallium nitride semiconductor used for a blue light emitting diode, a blue laser diode and the like and a method for growing the same.

[0002]

2. Description of the Related Art Gallium nitride (GaN) and indium gallium nitride (InGa) are practical semiconductor materials used for blue diodes, blue laser diodes and the like.
N) and gallium nitride-based compound semiconductors such as gallium aluminum nitride (GaAlN) have attracted attention. Among them, InGaN has a bandgap of 2 eV to 3.4 eV and thus is regarded as very promising.

Conventionally, metal organic chemical vapor deposition (hereinafter MOCV)
It is called D method. In the case of growing InGaN according to (4), it was grown on a sapphire substrate at a low growth temperature of 500 ° C to 600 ° C. Because the melting point of InN is about 5
Since 00 ° C and the melting point of GaN are about 1000 ° C,
When InGaN is grown at a high temperature of 600 ° C. or higher, In
This is because the decomposition pressure of InN in GaN becomes about 10 atm or more, and InGaN is almost decomposed, and only the deposits of Ga metal and In metal are formed. Therefore, in order to grow InGaN, the growth temperature had to be kept low.

[0004]

The crystallinity of InGaN grown under such conditions is very poor. For example, even when photoluminescence measurement is performed at room temperature, almost no band-to-band emission is observed and a deep quasi-state is obtained. Only a slight emission from the position was observed, and no blue emission was observed. Moreover, when trying to detect a peak of InGaN by X-ray diffraction, almost no peak was detected, and the crystallinity was closer to that of an amorphous crystal rather than a single crystal.

In order to realize blue light emitting devices such as blue light emitting diodes and blue laser diodes, it has been strongly desired to realize InGaN having high quality and excellent crystallinity. Therefore, the present invention has been made to solve this problem, and an object thereof is to provide InGaN having high quality and excellent crystallinity, and a growth method thereof.

[0006]

[Means for Solving the Problems]
When growing by the CVD method, nitrogen is used as a carrier gas of a source gas, and by growing on GaN or GaAlN instead of on sapphire as in the conventional case, excellent crystallinity can be obtained even at a temperature higher than 600 ° C. The present invention has been newly found out that the crystallinity and characteristics thereof can be remarkably improved by growing them while doping them with a specific element.

That is, the growth method of the present invention is a method for growing an indium gallium nitride compound semiconductor by the MOCVD method, wherein the source gas is a gallium source gas, an indium source gas, a nitrogen source gas, and a silicon source. of using a gas of a gas or germanium source, a further nitrogen carrier gas of the source gas, at a growth temperature higher than 600 ° C., on the gallium nitride layer, formula doped with Si or Ge in _X Ga _{1 -} It is characterized by growing an indium gallium nitride semiconductor represented by _X N (where X is 0 <X <0.5).

In the growth method of the present invention by the MOCVD method, the source gases are, for example, trimethylgallium {Ga (CH ₃ ) ₃ : TMG} as a Ga source, triethylgallium {Ga (C ₂ H ₅ ) ₃ : TEG}, Ammonia (NH ₃ ) and hydrazine (N ₂ H ₄ ) as nitrogen sources, trimethylindium {In (CH ₃ ) ₃ : TM as indium sources
I}, triethylindium {In (C ₂ H ₅ ) ₃ : TE
I}, silane (SiH ₄ ) as a silicon source, and germane (GeH ₄ ) as a germanium source can be preferably used.

Further, by using nitrogen as the carrier gas of the raw material gas, it is possible to prevent InN in InGaN from decomposing and going out of the crystal lattice even at a growth temperature higher than 600.degree.

The molar ratio of indium of the source gas of indium in the source gas supplied during the growth is as follows:
It is adjusted to preferably 0.1 or more, more preferably 1.0 or more. When the molar ratio of indium is less than 0.1,
Mixed crystals of InGaN are difficult to obtain, and the crystallinity tends to deteriorate. This is because the growth method of the present invention grows InGaN at a temperature higher than 600 ° C., so that some decomposition of InN occurs. Therefore, InN is less likely to enter the GaN crystal, and therefore it is possible to incorporate InN into the GaN crystal by preferably supplying more indium than the decomposed portion. Therefore, it is preferable to increase the molar ratio of indium as it grows at a higher temperature. For example, at a growth temperature of about 900 ° C., indium is supplied in an amount of 10 to 50 times that of gallium so that the X value becomes 0.
In _X Ga _1-X N having a ratio of less than 5 can be obtained.

The growth temperature may be higher than 600 ° C., and is preferably adjusted to a range of 700 ° C. or higher and 900 ° C. or lower. If the temperature is 600 ° C. or lower, it is difficult to grow a GaN crystal, and thus it is difficult to form an InGaN crystal, and even if it is formed, InGaN has poor crystallinity as in the conventional case.
Further, if the temperature is higher than 900 ° C., InN is likely to be decomposed, and InGaN tends to be GaN.

The molar ratio of the supplied indium gas and the growth temperature can be appropriately changed within the range of the target X value of In _X Ga _1-X N 0 <X <0.5. For example, in order to increase In, the growth may be performed at a low temperature of about 650 ° C., or the molar ratio of In in the source gas may be increased. If it is desired to increase the amount of Ga, it may be grown at a high temperature around 900 ° C. However, an In _X G to the X value at temperatures higher than 600 ° C. it is very difficult to grow a InXGaN1-XN to 0.5 or more, the X value of 0.5 or more
When a _1-X N is used in a light emitting device such as a light emitting diode, its emission wavelength is in the yellow region and it cannot be used for blue or ultraviolet light. did.

[0013]

FIG. 2 is a diagram showing the relationship between the supplied Si and the photoluminescence intensity of the Si-doped InGaN obtained in the growth method of the present invention. This is nitrogen at 2 liters / minute as carrier gas and TM as raw material gas.
G 2 × 10 ^-6 mol / min, TMI 20 × 10 ^-6 mol / min
, NH ₃ is supplied at a rate of 4 liters / minute, and Si is further doped. Therefore, the amount of silane gas supplied is changed to grow Si-doped In0.25Ga0.75N on the GaN layer.
After the growth, on the obtained Si-doped In0.25Ga0.75N layer,
Irradiate 10mW He-Cd laser, 450n
The photoluminescence intensity at m is measured. This figure shows relative intensity when the photoluminescence intensity of the In0.25Ga0.75N layer not doped with Si formed on the GaN layer is 1. This S
The photoluminescence spectrum of In0.25Ga75N not doped with i is shown in FIG. Separately, the photoluminescence spectrum of Si-doped In0.25Ga0.75N of the present invention is shown in FIG.

As shown in FIG. 2, the photoluminescence intensity of InGaN increases dramatically as Si is doped. By adjusting the molar ratio of silicon in the raw material gas to the range of 1 × 10 ^{−5 to} 0.05 with respect to gallium 1, the strength thereof is 5 compared to that not doped with Si.
It is more than doubled, and the maximum improvement is 60 to 70 times.

Similarly, FIG. 3 is a diagram showing the relationship between the supplied Ge and the photoluminescence intensity of the obtained Ge-doped In0.25Ga0.75N. Again, nitrogen is used as a carrier gas at 2 liters / minute and TMG is used as a source gas at 2 ×.
10 ^-6 mol / min, TMI 20 × 10 ^-6 mol / min, NH
₃ was supplied under the same conditions as 4 liters / minute, and the supply amount of germane gas was changed to dope Ge.
Ge-doped In0.25Ga0.75N was grown on the GaN layer, and after growth, the obtained Ge-doped In0.25Ga0.75N was obtained.
The photoluminescence intensity at 450 nm of the N layer is measured. This figure also shows the relative intensity when the photoluminescence intensity of the undoped In0.25Ga0.75N layer formed on the GaN layer is 1.

In FIG. 3 as well as FIG. 2, the photoluminescence intensity of InGaN dramatically increases as Ge is doped, and the molar ratio of germanium in the source gas is 1 × 10 ^{−4 to} 0 with respect to gallium 1. By adjusting to 0.5, the strength is 5 compared to that not doped with Si.
It can be seen that the number of times is more than double, and the maximum is also improved by 60 to 70 times.

By growing InGaN as described above, Si or Ge in InGaN is reduced to 10 ¹⁶ /
It can be doped with cm ³ to 10 ²² / cm ³ . From the photoluminescence result, the optimum value is 10 ¹⁸ to 10 ^20.
/ Cm ³ .

In the growth method of the present invention, by using nitrogen as the carrier gas of the source gas, decomposition of InGaN can be suppressed at a growth temperature higher than 600 ° C.,
Even if InN is decomposed to some extent, high quality InGaN can be obtained by supplying a large amount of indium in the source gas.

Further, conventionally, I is formed on a sapphire substrate.
I was growing an nGaN layer, but sapphire and InGa
Since the lattice constant irregularity is about 15% or more with N,
It is considered that the crystallinity of the obtained crystals deteriorates. on the other hand,
In the present invention, since the lattice constant irregularity can be reduced to 5% or less by growing it on the GaN or GaAlN layer, InGaN having excellent crystallinity can be formed. Figure 4 shows InG grown on a GaN layer.
It is aN, but it represents it remarkably, and in the conventional method,
The photoluminescence spectrum of InGaN could not be measured at all, but in the present invention, since the crystallinity is obviously improved, an emission peak appears in the blue region of 450 nm. In the growth method of the present invention, the Ga
A part of Ga of N may be replaced with Al, which is within the technical range.

Furthermore, by doping with Si or Ge, the photoluminescence intensity can be dramatically increased to 5 to 70 times as much as that without doping. This is due to the effect of Si and Ge, more crystalline,
It clearly shows that the quality is improved. Figure 5
FIG. 4 is a diagram showing this, which is obtained by measuring a spectrum in the range of 1/50 of FIG. 4, and it can be seen that the emission intensity is remarkably increased.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The growth method of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows the MOC used in the growth method of the present invention.
FIG. 3 is a schematic cross-sectional view showing the configuration of the main part of the VD device, showing the structure of a reaction part and a gas system diagram communicating with the reaction part. Reference numeral 1 is a reaction vessel connected to a vacuum pump and an exhaust device, 2 is a susceptor for mounting a substrate, 3 is a heater for heating the susceptor, 4 is a control shaft for rotating and vertically moving the susceptor, and 5 is a diagonal to the substrate. , Or a quartz nozzle that supplies the raw material gas horizontally, and 6 is a conical device that presses the raw material gas against the substrate surface by supplying the inert gas vertically toward the substrate to bring the raw material gas into contact with the substrate. A quartz tube, 7 is a substrate. TMG, T
The organic metal compound source such as MI is vaporized by a small amount of bubbling gas, and is supplied into the reaction vessel by a carrier gas which is a main gas together with a doping gas such as silane and germane.

Example 1 First, a well-cleaned sapphire substrate 7 is set on the susceptor 2, and the inside of the reaction vessel is sufficiently replaced with hydrogen.

Next, while flowing hydrogen from the quartz nozzle 5, the temperature is raised to 1050 ° C. by the heater 3 and kept for 20 minutes to clean the sapphire substrate 7.

Subsequently, the temperature was lowered to 510 ° C., while flowing 4 l / min of ammonia (NH ₃ ) from the quartz nozzle 5 and 2 l / min of hydrogen as a carrier gas,
Flow TMG at 27 × 10 ⁻⁶ mol / min and hold for 1 min.
The aN buffer layer is grown to about 200 Å. During this time, hydrogen is supplied from the conical quartz tube 7 to 10
Continue to flow liters / minute and nitrogen at 10 liters / minute and slowly rotate susceptor 2.

After the growth of the buffer layer, only TMG is stopped and the temperature is raised to 1030.degree. When the temperature reaches 1030 ° C, hydrogen is used as carrier gas and TMG is added to 54
Flowing at 10 ⁻⁶ mol / min for 30 minutes to grow the GaN layer to 2 μm.

After growing the GaN layer, the temperature is set to 800 ° C.
Switch the carrier gas to nitrogen and add 2 liters of nitrogen
Min, TMG 2 × 10 ^-6 mol / min, TMI 20 × 10
^-6 mol / min, silane gas at 2 × 10 ^-9 mol / min, and ammonia at 4 liters / min while Si-doped InG
Grow the aN layer for 60 minutes. During this time, the gas supplied from the conical quartz tube 7 is nitrogen only,
Continue to flow at l / min.

When the X-ray rocking curve of the InGaN layer obtained as described above was taken, it had a peak at a composition of In0.25Ga0.75N, and its half-value width was 6 minutes. This value of 6 minutes is the lowest value reported in the past, and shows that the crystallinity of InGaN by the method of the present invention is very excellent. Also, S
When Si in InGaN was measured by IMS,
It was 2 × 10 ¹⁹ / cm ³ .

[Embodiment 2] After the growth of the GaN layer, TMG is added to 2
A Ge-doped InGaN layer was grown in the same manner as in Example 1 except that the flow rate of x10 ^-6 mol / min, TMI of 20 × 10 ^-6 mol / min, and germane gas of 2 × 10 ^-8 mol / min were applied. .

When the obtained InGaN layer was irradiated with He—Cd laser and its photoluminescence was measured,
It had an emission peak at 450 nm, and when an X-ray rocking curve was measured, it had a peak at a composition of In0.25Ga0.75N, and its half-value width was also 6 minutes. Further, the Ge concentration in InGaN is about 1 ×.
It was 10 ¹⁹ / cm ³ .

[Example 3] After the growth of the GaN layer, the TMI was adjusted to 2
S was carried out in the same manner as in Example 1 except that the flow ^{rate was} × 10 ⁻⁷ mol / min.
An i-doped InGaN layer was grown.

When the X-ray rocking curve of the obtained InGaN layer was measured, it had a peak at the composition of In0.08Ga0.92N, and the half-value width was 6 minutes. When the photoluminescence of He-Cd laser was measured and the photoluminescence was measured at 390 nm, In
Interband emission of GaN was observed.

[Embodiment 4] After the growth of the buffer layer in Embodiment 1, only TMG is stopped and the temperature is raised to 1030.degree. When the temperature became 1030 ° C., likewise hydrogen 54 × 10 ^-6 mol / min and TMG as the carrier gas, by flowing TMA at 6 × 10 ^-6 mol / min was grown for 30 minutes, Ga0.
A Si-doped InGaN layer was grown on the Ga0.9Al0.1N layer in the same manner as in Example 1 except that the 9Al0.1N layer was grown to a thickness of 2 μm. As a result, the X-ray rocking curve of the obtained InGaN layer had a peak at the same composition of In0.25Ga0.75N, and the full width at half maximum was 6 minutes. The Si concentration was also the same as 2 × 10 ¹⁹ / cm ³ .

[0033]

According to the growth method of the present invention, it is possible to grow a single crystal of an InGaN layer, which has been impossible in the past, and the crystallinity and quality of Si and Ge are increased by growing the single crystal. Can be further improved. Therefore, since practical InGaN can be obtained by the present invention, a semiconductor material to be laminated on a blue light emitting device which will be developed in the future can be made into a double hetero structure, and a blue laser diode can be realized, and its industrial utility value is great. .

[Brief description of drawings]

FIG. 1 is an MO used in one embodiment of the growth method of the present invention.
The schematic sectional drawing which shows the structure of the principal part of a CVD apparatus.

FIG. 2 is a schematic diagram illustrating a method of supplying Si according to a growth method of the present invention;
The figure which shows the relationship of the photoluminescence intensity of obtained Si dope InGaN.

FIG. 3 shows the Ge supplied according to the growth method of the present invention,
The figure which shows the relationship of the photoluminescence intensity of the obtained Ge dope InGaN.

FIG. 4 shows InGa obtained by the process of one embodiment of the present invention.
The figure which shows the spectrum by the photoluminescence measurement of N.

FIG. 5 is a diagram showing a spectrum of InGaN measured by photoluminescence according to an example of the present invention.

[Explanation of symbols]

1 ... Reaction container 2 ... Susceptor 3 ... Heater 4 ... Control shaft 5 ...・ Quartz nozzle 6 ・ ・ ・ ・ ・ ・ ・ ・ Conical quartz tube 7 ・ ・ ・ ・ ・ ・ Substrate

Claims (6)

[Claims] 1. The general formula In _X Ga _1-X N (where X is 0 <X <
0.5) to the indium gallium nitride semiconductor represented by S)
An indium gallium nitride semiconductor characterized by being doped with i or Ge. 2. A method for growing an indium gallium nitride compound semiconductor by metalorganic vapor phase epitaxy, comprising a source gas containing a gallium source gas, an indium source gas, a nitrogen source gas, and a silicon source gas. using a germanium source gas, further carrier gas of the material gas as nitrogen, at temperatures above 600 ° C. growth temperature, on the gallium nitride layer, formula doped with Si or Ge an in _X G
a _1-X N (where X is 0 <X <0.5) is used to grow the indium gallium nitride semiconductor. 3. The method for growing an indium gallium nitride semiconductor according to claim 2, wherein the molar ratio of indium to gallium in the source gas is adjusted to 0.1 or more. 4. The method for growing an indium gallium nitride semiconductor according to claim 2, wherein the molar ratio of silicon to gallium in the source gas is adjusted to 1 × 10 ^{−5 to} 0.05. 5. The method for growing an indium gallium nitride semiconductor according to claim 2, wherein the molar ratio of germanium to gallium in the source gas is adjusted to 1 × 10 ^{−4 to} 0.5. 6. The method for growing an indium gallium nitride semiconductor according to claim 2, wherein the gallium nitride layer is a gallium aluminum nitride layer in which a part of gallium is replaced with aluminum.