JPH06196757A - Method of growing indium gallium nitride semiconductor - Google Patents

Abstract

PURPOSE:To obtain an InGaN having good quality and crystallizability by growing an indium gallium nitride layer on a gallium nitride layer at a specific growth temperature using a nitrogen as a carrier gas of a material gas. CONSTITUTION:By using a nitrogen as a carrier gas of a material gas, a decomposition of an InGaN can be controlled at a growth temperature of higher than 600 deg.C and even if some InN is decomposed, the InGaN with good quality can be obtained by supplying a large number of indium in the material gas. Also, by growing a buffer layer on a sapphire substrate at a low temperature before growing a GaN layer, a crystallizability of the GaN layer grown on the buffer layer is further improved and thus a crystallizability of the InGaN can be also improved. Therefore, since a semiconductor material stacked in a blue luminescent device can be formed in a double hetero structure, a blue laser diode can be implemented.

Description

Detailed Description of the Invention

[0001]

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

[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 conventionally, 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 a method for growing InGaN having high quality and excellent crystallinity.

[0006]

[Means for Solving the Problems]
When growing by the OCVD method, nitrogen is used as a carrier gas of a raw material gas at a high temperature of 600 ° C. or higher, and
The present invention has been newly found that the crystallinity of the GaN layer is remarkably improved by growing it on the GaN layer instead of on the sapphire substrate as in the past.

That is, in the growth method of the present invention, an indium gallium nitride semiconductor is grown by metalorganic vapor phase epitaxy using a gallium source gas, an indium source gas, and a nitrogen source gas as source gases. The method is to use nitrogen as a carrier gas for the raw material gas, and
An indium gallium nitride layer is grown on the gallium nitride layer at a higher growth temperature.

In the source gas, trimethylgallium (TMG) as a Ga source, triethylgallium (TEG), ammonia (NH ₃ ) as a nitrogen source, and hydrazine (N
₂ H ₄ ) and trimethylindium (T
MI), triethylindium (TEI) and the like can be preferably used.

Further, the molar ratio of indium of the indium source gas in the raw material gas supplied during the growth is preferably 0.1 or more, more preferably 1.0, relative to 1 gallium.
Adjust as above. If the molar ratio of indium is less than 0.1, it is difficult to obtain a mixed crystal of InGaN, and the crystallinity tends to deteriorate. Because the growth method of the present invention is 600
Since InGaN is grown at a temperature higher than 0 ° C., some decomposition of InN occurs. Therefore, InN is GaN
Since it is hard to enter the crystal, it is preferable to supply InN to the InN
It can be placed in the crystal of aN. 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 at about 10 to 50 times that of gallium, so that X
In _X Ga _1-X N having a value of less than 0.5 can be obtained.

Furthermore, by using nitrogen as the carrier gas for these source gases, it is possible to prevent InN in InGaN from decomposing and going out of the crystal lattice.

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 indium gas and the growth temperature can be appropriately changed depending on the target indium molar ratio of InGaN. For example, to increase In, it is necessary to grow at a low temperature of about 650 ° C., or to increase the molar ratio of In in the source gas, while to increase Ga, grow at a high temperature of around 900 ° C. Good.

[0013]

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

Further, in the past, I was 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 layer, InGaN having excellent crystallinity can be formed. FIG. 2 shows InGaN obtained according to an embodiment of the present invention.
It is the photoluminescence spectrum of, but it is remarkable. In the conventional method, the blue spectrum of InGaN photoluminescence 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, a part of Ga of GaN may be replaced with Al, which is within the technical range.

[0015]

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 organometallic compound source such as MI is vaporized by a small amount of bubbling gas and supplied into the reaction vessel by the carrier gas which is the main gas.

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 liters / minute of ammonia (NH ₃ ) from the quartz nozzle 5 and 2 liters / minute 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 continuously flowed from the conical quartz tube 7 at 5 l / min and nitrogen is continued at 5 l / min, and the susceptor 2 is slowly rotated.

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, InGaN is grown for 60 minutes while flowing ammonia at 4 l / min. During this time,
The gas supplied from the conical quartz tube 7 is also nitrogen, and the flow is continued at 10 liters / minute.

After the growth, the wafer was taken out from the reaction container, the InGaN layer was irradiated with a 10 mW He—Cd laser, and the photoluminescence measurement was carried out at room temperature.
As shown in FIG. 5, strong blue light emission having a peak at 450 nm was exhibited.

Further, when the X-ray rocking curve of the InGaN layer was taken, it had a peak at a composition of In0.25Ga0.75N, and the half-width was 8 minutes. This value of 8 minutes is the minimum value reported in the past, and shows that the crystallinity of InGaN by the method of the present invention is very excellent.

[Example 2] InGaN was grown in the same manner as in Example 1 except that the TMI flow rate was set to 2 x 10 ^-7 mol / min when InGaN was grown after the GaN layer was grown.
Grow. When the X-ray rocking curve of this InGaN was measured, a peak appeared at the composition of In0.08Ga0.92N, and the half value width was 6 minutes.

[Embodiment 3] 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.
An 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 half-width was 8 minutes.

[Comparative Example] After cleaning the sapphire substrate in the same manner as in Example, the temperature was set to 800 ° C., hydrogen as a carrier gas was 2 liter / min, and TMG was 2 × 10 5.
InGaN is grown on the sapphire substrate for 60 minutes while flowing ^-6 mol / min, TMI of 20 × 10 ^-6 mol / min and ammonia of 4 liter / min. During this period, the conical quartz tube 7 is continuously supplied with nitrogen at 5 l / min and hydrogen at 5 l / min.

Photoluminescence measurement of InGaN grown in the above manner was carried out in the same manner as shown in FIG.
Shown in. As you can see from this figure, this InGaN
The light of the deep level of 550 nm is dominant in the crystal of.
Moreover, this emission center is generally considered to be a vacancy of nitrogen, and it is clear that InGaN has not grown. Therefore, as far as this result is seen, it seems that most of InGaN is decomposed in the form of InN during the growth and slightly grown in the form of GaN.

To confirm this, the X-ray rocking curve was measured in the same manner, and the full width at half maximum was about 1.
It was found that the peak position was near GaN and the crystal was not InGaN but GaN was amorphous.

[0028]

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. Further, by growing the buffer layer on the sapphire substrate at a low temperature before growing the GaN layer, the crystallinity of the GaN layer grown thereon is further improved,
The crystallinity of InGaN can also be improved.

As described above, according to the growth method of the present invention, since the semiconductor material laminated on the blue light emitting device to be developed in the future can have a double hetero structure, a blue laser diode can be realized and its industrial utility value is high. large.

[Brief description of drawings]

FIG. 1 MOCV used in one embodiment of the method of the present invention
FIG. 3 is a schematic cross-sectional view showing the configuration of the main part of the D device.

FIG. 2 is an InGa formed according to an embodiment of the present invention.
The figure which measured the photoluminescence of N.

FIG. 3 is a diagram in which the photoluminescence of InGaN formed by a conventional method is measured.

[Explanation of symbols]

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

Claims (3)

[Claims] 1. A gallium source gas as a source gas,
In a method of growing an indium gallium nitride semiconductor by a metalorganic vapor phase epitaxy using a gas of an indium source and a gas of a nitrogen source, nitrogen is used as a carrier gas of the raw material gas, and 600
A method for growing an indium gallium nitride semiconductor, which comprises growing an indium gallium nitride layer on a gallium nitride layer at a growth temperature higher than ° C. 2. The method for growing an indium gallium nitride semiconductor according to claim 1, wherein the molar ratio of indium to gallium in the source gas is adjusted to 0.1 or more. 3. The method for growing an indium gallium nitride semiconductor according to claim 1, wherein the gallium nitride layer is a gallium aluminum nitride layer in which a part of gallium is replaced with aluminum.