JP3077781B2 - Method for growing indium gallium nitride - Google Patents

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 indium gallium nitride used for light emitting diodes, laser diodes and the like.

[0002]

2. Description of the Related Art Generally, the band gap energy (Eg) of In _x Ga ₁ -xN is 3.4 when X is in the range of 0 ≦ X ≦ 1.
It is known to change from eV to 2.0 eV (Jo
unal of Applied Physics; Vol. 46, No. 8, 1975, 3432
~).

[0003] As a method of growing InGaN,
For example, MOCVD (Metal Metal Vapor Deposition)
Organic Chemical Vapor Deposition method. According to this method, InGaN 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 500 ° C,
Since the melting point of GaN is approximately 1000 ° C.,
When InGaN is grown at the above high temperature, the decomposition pressure of InN in InGaN becomes about 10 atm or more, and InG
aN is almost completely decomposed, and what is formed is Ga
This is because only deposits of the metal of In and the metal of In are formed. Therefore, conventionally, when growing InGaN, the growth temperature had to be maintained at a low temperature.

InGaP grown under such conditions
The crystallinity of N is very poor. For example, even if photoluminescence measurement is performed at room temperature, emission between bands is hardly observed, emission from a deep level is only slightly observed, and blue emission is observed. I never did. And X
Even if an attempt was made to detect the peak of InGaN by line diffraction, almost no peak was detected, and the crystallinity was closer to an amorphous crystal rather than a single crystal.

Recently, 500 ° C. to 8 ° C.
It has been reported that InGaN was grown on a sapphire substrate at 00 ° C. (Applied Physics Letter; Vol. 59,
No 28, 1991, 2251-). According to this report, by supplying a large amount of ammonia, which is a nitrogen source, and In gas, InGaN grown at 800 ° C. does not become a metal deposit, and is more intense than that grown at 500 ° C. It shows that the crystallinity is improved. However, the crystallinity of the obtained InGaN is still poor, and InG
Light emission between bands of aN was not observed at room temperature, and light emission from a deep level was dominant. Further, the growth temperature 6
At a temperature of 00 ° C. or higher, InN is easily decomposed, so that the X value is set to 0.1.
It has been difficult to grow In _x Ga ₁ -xN of 2 or more.

[0006]

In order to obtain a light emitting device such as a light emitting diode or a laser diode, the material forming the light emitting element must have high quality and excellent crystallinity. In In _X Ga _{1 -X} N, the band gap energy changes by arbitrarily changing the X value, and the emission wavelength is changed from 365 nm to 6 nm.
Although there is a range of 20 nm, it has not yet been reported that InGaN having excellent crystallinity that can be used as a light emitting material has been obtained.

Accordingly, the present invention has been made in view of such circumstances, and it is an object of the present invention that the X value is 0.
In _x Ga _1-x N can be grown in the range of <x <1, and
An object of the present invention is to provide a method for growing InGaN having excellent crystallinity and capable of obtaining strong interband emission of nGaN.

[0008]

According to the method of growing InGaN of the present invention, the general formula In _x Ga ₁ -xN (where X is 0 <X <1)
In the method of growing indium gallium nitride represented by the following formula, the gallium nitride is grown using hydrogen as a carrier gas for the source gas, and then the carrier gas for the source gas is used as nitrogen. The method further comprises growing the indium gallium nitride and irradiating the growth surface with an electromagnetic wave having an energy larger than the band gap energy of the indium gallium nitride to be grown.

The band gap energy (Eg) of In _x Ga ₁ -xN is determined experimentally and can be calculated, for example, by the following equation (Jounal of Applied Physic).
s; Vol. 46, No. 8, 1975, 3432-). Eg = EgGaN ・ (1-X) + EgInN ・ (X) -BX ・ (1-X) where EgGaN is 3.4 eV in GaN band gap energy, EgInN is 2.0 eV in InN band gap energy, B is a Boeing parameter, which is about 1.0 eV. For example, to grow In _x Ga ₁ -xN with an X value of 0.4 or more,
Eg of n0.4Ga0.6N is 2.6 eV and 2.6 eV
Has a band gap energy of about 477
In _X Ga ₁ -XN having an X value of 0.4 or more can be grown by irradiating an electromagnetic wave (for example, ultraviolet light) having a wavelength shorter than 477 nm. However, it goes without saying that during the growth, the molar ratio of the gas of the indium source to the gallium is set to 0.4 or more.

[0010] Examples of the electromagnetic wave irradiated during the growth of InGaN include InN bandgap energy of 2.0 eV, that is, visible light, ultraviolet light, and X-rays having a wavelength shorter than 620 nm. Among them, as a preferable light source, a visible light, a high-pressure mercury lamp emitting ultraviolet light, a xenon lamp, a lamp such as an ultraviolet lamp, or the like can be used, and the light from these light sources can be condensed by a lens and irradiated to the growth surface. . A light source having a wide emission band such as a xenon lamp can be adjusted to a desired wavelength or less by passing through a filter.

As a source gas used in the MOCVD method, for example, an organic metal compound gas such as trimethyl gallium (TMG) or triethyl gallium (TEG) as a gallium source, trimethyl indium (TMI) or triethyl indium (TEI) as an indium source, or nitrogen. As a source, gases such as ammonia (NH ₃ ) and hydrazine (N ₂ H ₄ ) can be preferably used, and these gases are mixed with a carrier gas, and the mixture is injected toward a heated substrate to grow InGaN. Can be done. S on the substrate
iC, Si, ZnO, sapphire and the like can be used, but usually sapphire is used.

Preferably, the growth temperature is adjusted in the range of 600 ° C. to 900 ° C. Even at temperatures lower than 600 ° C, In
Although it is possible to grow GaN, if the temperature is 600 ° C. or lower as described above, it is difficult to grow GaN crystals, and it is difficult to form InGaN crystals. InGaN tends to be InGaN, and if the temperature is higher than 900 ° C., InN is easily decomposed, so that InGaN tends to be GaN. In the case where the growth is performed within the above-mentioned growth temperature range, by using nitrogen as the carrier gas of the source gas, decomposition of InN can be suppressed and InGaN with good crystallinity can be obtained.

[0013] Furthermore, when InGaN is grown on GaN rather than directly on a substrate, the lattice constant irregularity can be reduced, so that InGa having excellent crystallinity can be obtained.
N is obtained.

[0014]

FIG. 1 shows an InO. Layer grown at a growth temperature of 700 ° C. on a GaN layer by MOCVD under UV irradiation.
FIG. 4 is a diagram in which 4Ga0.6N is irradiated with a He-Cd laser at room temperature, and its photoluminescence spectrum is measured. On the other hand, FIG. 2 is a spectrum diagram of the photoluminescence of In0.4Ga0.6N grown at a growth temperature of 500 ° C. on a sapphire substrate without UV irradiation.

As can be seen by comparing these figures, U
In0.4Ga0.6N grown by V irradiation has strong interband emission at the position of bandgap energy (around 475 nm) according to its composition ratio, but In0.4Ga0.6N obtained by the conventional method. .6N has poor crystallinity and In
No inter-band light emission of GaN can be detected at all, indicating that light emission from deep levels is dominant. Note that the emission intensity on the vertical axis in FIG. 2 is obtained by magnifying the emission intensity in FIG. 1 by 20 times, and this also shows how excellent the crystallinity of InGaN according to the method of the present invention is.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The growth method of the present invention will be described below in detail with reference to the drawings. FIG. 3 shows the MOC used in the growth method of the present invention.
FIG. 2 is a schematic cross-sectional view illustrating a configuration of a main part of the VD apparatus, illustrating a structure of a reaction unit and a gas system diagram communicating with the reaction unit. 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 axis for rotating and moving the susceptor up and down, and 5 is a diagonal toward the substrate. Or a quartz nozzle for supplying the source gas horizontally, and a conical nozzle 6 for supplying the inert gas vertically toward the substrate, thereby pressing the source gas against the substrate surface and bringing the source gas into contact with the substrate. A quartz tube, 7 is a substrate, and 8 is a light source for irradiating light from above the conical quartz tube 7 toward the substrate 7, mainly 436 nm, 405 nm,
A 200 W ultra-high pressure mercury lamp that emits light of 365 nm is installed, and has a structure in which the light is focused by the lens 9 and can uniformly irradiate the substrate 7. The source of an organometallic compound such as TMG or TMI is vaporized by a slight amount of bubbling gas and supplied into the reaction vessel by a carrier gas as a main gas. Although not particularly shown, the flow rates of each source gas and carrier gas are controlled by a mass flow controller (MFC) installed in each gas line.

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

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

Subsequently, the temperature was lowered to 510 ° C., and ammonia (NH ₃ ) 4 L / min.
MG is 27 μmol / min, and hydrogen is 2 as a carrier gas.
While flowing at a rate of 1 liter / minute, the GaN buffer layer is maintained for 1 minute to grow the GaN buffer layer to about 200 angstroms. During this time, hydrogen is continuously supplied from the conical quartz tube 7 at 10 L / min and nitrogen is supplied at 10 L / min, and the susceptor 2 is slowly rotated. During this time, the gas supplied from the conical quartz tube 7 is also nitrogen, and the gas is kept flowing at 20 liter / min.

After the growth of the buffer layer, only TMG is stopped, and the temperature is increased to 1020 ° C. When the temperature reaches 1020 ° C., hydrogen is also used as a carrier gas and TMG is
Growing at a flow rate of μmol / min for 30 min.
grow by μm.

After growing the GaN layer, the temperature is increased to 700 ° C.
Switch the carrier gas to nitrogen and use 2 liters of nitrogen /
At the same time, TMG is flowed at 2 μmol / min, TMI is flowed at 2 μmol / min, and ammonia is flowed at 4 liter / min. At the same time, InGaN is grown for 60 minutes while the light source 8 is turned on and the substrate 7 is irradiated.

After the growth, the wafer is taken out of the reaction vessel, and the InGaN layer is irradiated with a 10 mW He-Cd laser to perform photoluminescence measurement at room temperature.
Strong inter-band emission of In0.4Ga0.6N was observed around 5 nm.

Example 2 After growing the GaN layer, InGaN was grown in the same manner as in Example 1 except that the growth temperature was changed to 650 ° C. and the flow rate of TMI was changed to 20 μmol / min. The photoluminescence of the obtained InGaN was measured in the same manner as in Example 1, and as a result, I
Strong interband emission of n0.7Ga0.3N was shown.

Comparative Example 1 InGaN was grown in the same manner as in Example 1 except that the light source 8 was not turned on. When the spectrum of the photoluminescence of the obtained InGaN was measured, light emission from a broad deep level was observed around 550 nm, and no inter-band light emission could be observed. When the X-ray rocking curve of InGaN was measured to confirm the crystallinity, no peak of InGaN could be detected, and it was found from the half-value width that the crystal was amorphous.

Comparative Example 2 InGaN was grown in the same manner as in Example 2 except that the light source 8 was not turned on. As a result of performing photoluminescence measurement of the obtained InGaN in the same manner as in Example 1, no light emission was observed at room temperature.

As can be seen from the comparison between Example 1 and Comparative Example 1 and between Example 2 and Comparative Example 2, UV irradiation at the same growth temperature as in the present invention increases the In ratio and increases the crystallinity. InGaN having excellent properties can be grown.

As described above, InGaN has a growth temperature of 750
When the temperature drops to 650 to 650 ° C, I
It is considered that the reaction of the atoms of n, Ga, and N becomes difficult to progress, and the crystallinity deteriorates. In order to supplement this heat energy, another energy is newly supplied by an electromagnetic wave as in the present invention, so that the atomic species on the substrate surface can be made more active to facilitate the reaction, and the In ratio can be increased. InG
It is presumed that aN can be grown. In addition, irradiation of an electromagnetic wave larger than the band gap energy causes light absorption in InGaN to generate electrons and holes, and the electromagnetic waves are converted into In, Ga, and
It is thought that it is transmitted to the atomic species of N to promote the activation of these atomic species.

[0028]

As described in the foregoing, In _X Ga in _1-X N growth, by irradiating an electromagnetic wave having energy larger than the band gap energy of the InGaN during the growth, In ratio of large an In _X Ga _1-X N can be grown. Further, the obtained In _x Ga ₁ -xN shows strong interband emission and has excellent crystallinity so that it can be sufficiently used as a light emitting element. Therefore, by using the method of the present invention, 365 nm to 620
It is possible to realize a light emitting device having an emission wavelength of nm.

[Brief description of the drawings]

FIG. 1 shows InGaN obtained according to one embodiment of the present invention.
FIG. 3 is a spectrum diagram of the photoluminescence measurement of FIG.

FIG. 2 is a spectrum diagram of photoluminescence measurement of InGaN obtained by a conventional method.

FIG. 3 is a schematic sectional view showing a configuration of a main part of an MOCVD apparatus used in one embodiment of the present invention.

[Explanation of symbols]

1 ······ Reaction vessel 2 ······························ Heater 4 ·············· · Quartz nozzle 6 ······ Conical quartz tube 7 ····· Substrate 8 ····· Light source 9 ····· Lens

Continuation of front page (56) References JP-A-1-164895 (JP, A) JP-A-1-215014 (JP, A) JP-A-4-297023 (JP, A) Appl. Phys. 60 (9), 1 November 1986, pp. 3131-3135 Jpn. J. Appl. Phys. vol. 29, No. 2, February 1990, p. L225-L228 (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 H01L 21/31 H01L 33/00 H01S 5/30

Claims (2)

(57) [Claims] 1. The general formula In _x Ga ₁ -xN (where X is 0 <X <
In the method of growing indium gallium nitride represented by 1) by a metalorganic chemical vapor deposition method, gallium nitride is grown using hydrogen as a carrier gas as a source gas, and then the gallium nitride is used as a carrier gas as a source gas as nitrogen. Growing the indium gallium nitride thereon, and irradiating the growth surface with an electromagnetic wave having an energy larger than the band gap energy of the indium gallium nitride to be grown. 2. The growth temperature of the indium gallium nitride is 600 ° C. to 900 ° C.
3. The method for growing indium gallium nitride according to item 1.