JP2000216096A - Chemical vapor deposition method of gallium indium nitride crystal layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemical vapor deposition method whereby a gallium indium nitride crystal layer having a multi-phase structure contg. microcrystals functioning as quantum boxes or quantum dots as a subordinate phase can be efficiently formed. SOLUTION: The chemical vapor deposition method is as follows. On a substrate a gallium indium nitride (GaxIn1-xN: 0<=x<1) crystal layer is formed by the org. metal thermal composition vapor phase deposition method using cyclopentadienyl In (C5H5In(I)) having a monovalent bond as an In material with an org. Si compd. added 0.1-100 wt.ppm as converted in Si element concn. as an impurity at the same time to the In material. The gallium indium nitride crystal layer is formed in contact with a III group compd. semiconductor layer formed on the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a vapor phase growth method using an organic indium compound as an indium raw material, for example, a high-performance II such as a high-luminance group III nitride semiconductor light emitting device.
The present invention relates to a technique for forming a gallium indium nitride crystal layer suitably used for manufacturing a group I nitride semiconductor device.

[0002]

2. Description of the Related Art A gallium indium nitride crystal layer is commonly used as an active layer (light emitting layer or well layer).
The prior art will be described using a group III nitride semiconductor light emitting device as an example. Group III nitride semiconductor light emitting devices such as light emitting diodes (LEDs) and laser diodes (LDs) that emit short-wavelength light from the red-orange band to the ultraviolet band emit light called a well layer or a light-emitting layer. The active layer that carries the
n-type gallium indium nitride (Ga _X In _{1 -X} N:
0 ≦ X <1 (JP-B-55-383)
No. 4). This depends on the adjustment of the indium composition ratio (1-X), and the gallium indium nitride crystal has about 3%.
This is because a favorable band gap for obtaining light emission from the near ultraviolet band from 60 nanometers (nm) to about 560 nm to the short wavelength visible light band can be obtained.

[0003] A pn junction type double heterostructure (Double)
In a light-emitting portion having a Hetero: DH) junction structure, a gallium-indium nitride active layer is sandwiched between p-type and n-type barrier layers (cladding layers) (see JP-A-6-260283). Single quantum well structure (SQ
In the case of W) or the multiple quantum well structure (MQW), the gallium-indium nitride active layer is formed by being joined to a barrier layer (barrier layer). In terms of crystallographic structure, gallium nitride with a uniform and single indium composition
There is a conventional example in which an active layer (light emitting layer or well layer) is formed from indium (see Japanese Patent Application Laid-Open No. 9-36430).

Conventionally, gallium indium nitride has been formed exclusively by a metal organic chemical vapor deposition (MOCVD) method using an organic indium compound as an indium (In) raw material. Organic indium compounds include Lewis acidic trimethylindium ((CH
₃ ) ₃ In) is generally used. Lewis, a monovalent valent as a unique indium raw material
Basic cyclopentadienyl indium (C ₅ H ₅
There is also a prior art example using In (I) (Japanese Patent Publication No.
-17160 and JP-A-10-22224). By the way, as a nitrogen raw material, Lewis
Basic ammonia (NH ₃ ) is generally used (for example, see JP-A-2-229476).

[0005] In a conventional configuration, the gallium indium nitride active layer is formed by bonding it to a barrier layer made of aluminum gallium nitride (AlGaN). MO
In the CVD method, aluminum gallium nitride is generally
The film is formed at a high temperature of about 1000 ° C. or higher (“Optics”, Vol. 22, No. 11, November, 1993)
670-675). On the other hand, the gallium indium nitride active layer is usually formed at a lower temperature than aluminum gallium nitride in order to suppress the loss due to its easy sublimation (JP-A-6-209122).
No. 2751987). The gallium-indium nitride active layer is formed at a temperature of 500 ° C.
To 800 ° C from the conventional technology example (Appl.
hys. Lett. , 59 (18) (1991), 22
51 to 2253), usually from 650 ° C to 900 ° C
(See Japanese Patent No. 2751987).

Recent technical achievements regarding the structure of a gallium indium nitride crystal layer suitable as an active layer include a quantum structure such as a quantum box or a quantum dot (dot) structure resulting from the generation of a region having a different indium composition. (See Japanese Patent Application Laid-Open No. 10-107314) is also preferable because high-intensity light emission can be obtained (Japanese Patent Application Laid-Open Nos. 10-145000 and 10-107314).
No. 145002).

A gallium indium nitride crystal layer composed of regions having different indium concentrations is a so-called multiphase gallium indium nitride crystal layer composed of a plurality of phases having different indium compositions (domain or phase). (See JP-A-10-56202). A polyphase structure occupies a large area in space,
The main phase (matrix phas) mainly constituting the crystal layer
In other words, e) is a mixture of a main phase and a subphase that forms a microcrystal having a different indium composition ratio, which is dependent on the main phase and can be expected to act as a quantum dot. You. Gallium indium nitride is originally a material that easily causes phase separation (Appl. Phys. Let.
t. , 70 (8) (1997), pp. 981 to 983), and gallium indium nitride having a multiphase structure has an advantage that a film can be easily formed.

[0008]

SUMMARY OF THE INVENTION Low-di
Quantum structures such as quantum boxes or quantum dots that provide general carriers are provided by the microstructure of the gallium indium nitride crystal layer.
For example, a quantum dot is made of a microcrystalline material having a diameter of approximately several tens angstroms (Å) existing in a main phase of a gallium indium nitride crystal layer.
-107314). Therefore, in order to form a gallium indium nitride active layer having a quantum structure including quantum dots, a crystal layer to be an active layer is formed by a method capable of conveniently generating microcrystals having a size suitable for acting as a quantum dot. Need to be formed.

However, the problem of the MOCVD method, which is a typical method for growing a conventional gallium-indium nitride active layer, is omitted. There is a problem that growth is hindered. In particular, a typical indium raw material (CH ₃ ) ₃
In and ammonia, which is a common nitrogen source, easily react in the gas phase to form a complex (polymer) (IEICE Technical Report CPM 84-122).
(1984), pp. 1-6). When such a high molecular weight high molecular substance is formed, a crystal fine enough to exhibit the quantum effect is stably formed in the gallium indium nitride crystal layer with a substantially uniform particle size. It cannot be formed. The size of the microcrystal as a quantum dot is said to affect the threshold voltage in a laser diode, and the uneven size of the quantum dots is considered to have an adverse effect on the reduction ("Laser Research"). , Vol. 25, No. 7, July 1997, 498-5
See page 03).

In order to stably obtain an active layer composed of a gallium-indium nitride crystal layer containing a microstructure such as a quantum dot, the size (diameter) of the microcrystal must be increased.
It is a matter of course that the gallium-indium nitride crystal layer is formed by a growth technique capable of avoiding a complexing reaction between the raw materials of the group I and group V constituent elements. General MOCV using Lewis basic ammonia as nitrogen source
In the method D, the indium raw material is the same Lewis basic cyclopentadienyl indium (C ₅ H ₅ In
It has already been taught that if (I)), the polymerization reaction can be prevented (see Japanese Patent Publication No. 8-17160).
However, in order to efficiently obtain a gallium-indium nitride crystal layer having a multiphase structure, the requirements that the above-mentioned cyclopentadienylindium as an indium raw material should have, such as the types of impurities to be added at the same time and the concentrations thereof, are still unknown. It has not been disclosed.

It is an object of the present invention to provide a gallium-indium nitride crystal layer having a multiphase structure containing a microcrystal as a subordinate phase by using a raw material system which does not cause a complexing reaction in a gas phase and an organometallic heat treatment. An object of the present invention is to provide a vapor phase growth method for stably forming by a decomposition vapor phase growth method (MOCVD method). Another object of the present invention is to provide a means for stably forming an active layer composed of a gallium / indium nitride crystal layer having a multiphase structure and having a structure capable of exhibiting an action as a quantum dot or a quantum box. The object of the present invention is to overcome this problem and to achieve high performance of high-luminance group III nitride semiconductor light-emitting devices based on the presence of low-dimensional carriers, for example.
An object of the present invention is to provide a gallium-indium nitride crystal layer suitably used for manufacturing a group III nitride semiconductor device.

[0012]

That is, according to the first aspect of the present invention, in a vapor phase growth method of a gallium indium nitride crystal layer by a metalorganic thermal decomposition vapor phase growth method, a valence is formed on a substrate. the use monovalent cyclopentadienyl indium is _{(C 5 H 5 in (I} )) to the indium source, the indium source relative to the to 0.1 ppm by weight to a concentration of silicon (Si) element organic While simultaneously adding a silicon compound as an impurity, gallium indium nitride (Ga _x In _{1 -x}
N: 0 ≦ X <1) A vapor phase growth method of a gallium indium nitride crystal layer, characterized by forming a crystal layer.

According to a second aspect of the present invention, in addition to the first aspect, the gallium-indium nitride crystal layer comprises a main phase mainly comprising a crystal layer, and the main phase comprises indium (In). A) a vapor phase growth method for a gallium indium nitride crystal layer, characterized in that it has a multiphase structure comprising different composition ratios and a dependent phase mainly composed of microcrystals.

According to a third aspect of the present invention, in addition to the first or second aspect, the gallium-indium nitride crystal layer is in contact with a group III nitride semiconductor layer formed on the substrate. A method for vapor-phase growth of a gallium-indium nitride crystal layer, which is formed.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in a vapor phase growth method of a gallium indium nitride crystal layer by a metalorganic thermal decomposition vapor phase growth method, cyclopentadienyl indium (C ₅ H ₅₎ having a monovalent valence is used. In (I) (CpIn)) is used as an indium raw material. Since cyclopentadienyl indium has unpaired electrons, Lewis (L
ewis) because it exhibits basicity and does not easily bond to Lewis basic substances such as ammonia, which is a common nitrogen source, that is, does not cause a gas phase complexation (polymerization) reaction. For this reason, it is possible to avoid the formation of large aggregates having a large molecular weight due to polymerization, which is inconvenient for providing a quantum effect, and to reduce the number of gallium indium nitride crystal layers by depositing such large aggregates. It is possible to prevent the phase structure from being disordered. In other words, there is an effect that a gallium-indium nitride crystal layer having a multi-phase structure having a low density of large foreign substances (aggregates) and excellent crystallinity can be formed.

The poor bondability of cyclopentadienylindium to ammonia, which is exhibited by the presence of unpaired electrons, is also exhibited under normal pressure (substantially atmospheric pressure).
Therefore, cyclopentadienyl indium is not required for the intervening reaction (s) even in the vapor phase growth method of the gallium indium nitride crystal layer by the metalorganic pyrolysis vapor phase growth method at normal pressure.
normal-pressure MO
It is useful as an indium raw material in the CVD method. When forming an easily sublimable gallium indium nitride crystal layer, growing the crystal layer under normal pressure is particularly advantageous in preventing the crystal layer from being damaged by sublimation or thermal dissociation. Therefore, cyclopentadienyl indium is a good quality gallium indium nitride (Ga _X In _{1 -X} N: 0 ≦ X <1).
It is an indium raw material that allows a crystal layer to be vapor-phase grown by atmospheric pressure MOCVD.

The vapor pressure of cyclopentadienylindium can be known from a previous report (Yasuo Kuniya, 19
Proceedings of the 50th Annual Meeting of the Japan Society of Applied Physics Academic Lecture, Autumn 1989, first volume, 315 pages, see lecture number 30a-W-9).
When forming the Ga _x In ₁ -xN crystal layer by the atmospheric pressure MOCVD method, the cyclopentadienyl indium raw material is so formed that the cyclopentadienyl indium emits a vapor pressure of at least about 0.05 Torr. Preferably, the container is kept at a constant temperature. The sublimated cyclopentadienyl indium is transported into a reaction furnace for growing a crystal layer by MOCVD using an accompanying gas such as hydrogen (H ₂ ), nitrogen (N ₂ ), or argon (Ar).

Further, while avoiding thermal damage of the Ga _x In _1-x N crystal layer due to sublimation, Ga _x
In order to efficiently form an In _1-X N crystal layer, it is convenient to use a reactor equipped with a mechanism capable of adjusting the volume of a portion where a raw material gas or the like flows directly above a substrate to be used (for example, see Patent No. 2828708). Especially atmospheric pressure MOCVD
In the method, it is advantageous that the volume of the above-mentioned portion is reduced as much as possible so as not to adversely affect the uniformity of the thickness of the growing crystal layer or the carrier concentration.

FIG. 5 shows a supply system in which a cyclopentadienyl indium storage container for connecting the cyclopentadienyl indium vapor to the accompanying gas at a high concentration substantially uniformly in the accompanying gas is provided together with a supply system connected directly above the substrate. 1 schematically illustrates a reactor for growing a crystal layer by a normal pressure MOCVD method having a mechanism capable of adjusting a volume. The accompanying gas for transporting the vapor of the cyclopentadienyl indium 10 flows into the first storage container 10a that stores the cyclopentadienyl indium 10. First storage container 10
a, and the associated gas containing the vapor of cyclopentadienyl indium 10 is supplied to the first storage container 10
It is introduced into the second storage container 10b connected in series to the outlet of the associated gas of a. The accompanying gas that has flowed into the second storage container 10b accompanies the sublimated vapor of cyclopentadienylindium that fills the container 10b. Therefore, in the supply system having a plurality of indium source containers, as compared with a supply system using a single source container as a supply source, as a result, the accompanying gas containing cyclopentadienylindium vapor at a constant high concentration is subjected to MOCVD.
It can be supplied to the reaction zone 30 of the reactor 20. Reaction area 30
In the figure, the substrate 23 is placed on the susceptor 22 which is superior in ensuring uniformity. The temperature of the substrate 23 is heated to a desired temperature by a heating body 24 such as a high-frequency induction coil disposed below the susceptor 22, and the temperature can be lowered at an appropriate speed by adjusting the amount of electric power to be supplied. A partition 25 is provided above the susceptor 22. The partition 25 is provided to limit the flow path in the reactor 20 of the accompanying gas and the carrier gas accompanying the raw material supplied from the gas introduction hole 21 provided at the top of the reactor 20. In addition, a mechanism 27 is provided that can adjust the distance 26 between the substrate 23 and the partition wall 25 by moving the susceptor 22 up and down. If the interval 26 is reduced, the volume of the portion immediately above the substrate 23 is reduced. If this volume is reduced, the concentration of the nitrogen source or the indium source in the region above the substrate can be kept high, so that the effect of preventing thermal degradation of the Ga _x In ₁ -x N crystal layer can be obtained. By appropriately shortening the interval 26, the loss due to the sublimation of Ga _X In _1-X N is suppressed, and the uniformity of the film quality is deteriorated due to the thermal convection of the accompanying gas accompanying the raw material and the carrier gas. There is an advantage that can be suppressed. Ga _x In by atmospheric pressure MOCVD
The formation of the _1-X N crystal layer depends on the total amount of gas supplied into the reaction furnace 20 through the gas introduction holes 21. From 800 ° C. to 900 ° C., uniformity of the crystal layer thickness and the like can be ensured, and G can be obtained without causing thermal damage.
The range of the spacing 26 that results in the formation of the a _X In _1-X N crystal layer is in the range of approximately 5 mm to 15 mm.

The gallium-indium nitride crystal layer is composed of a multi-phase comprising a main phase mainly constituting the crystal layer, and a sub-phase different from the main phase in indium (In) composition ratio and mainly consisting of microcrystals. When constituted by a structure, the dependent phase composed of a microcrystal forms a quantum structure that is convenient for generating low-dimensional carriers such as a quantum box or a quantum dot structure. M using cyclopentadienylindium having a monovalent valence as an indium raw material and ammonia as a nitrogen raw material
In order to form the gallium indium nitride crystal layer having a multiphase structure by the OCVD method, the growth temperature of the crystal layer is preferably in a range of about 700 ° C. to about 950 ° C. A more desirable growth temperature is above 750 ° C.
It is below ° C. Particularly, in the growth of a Ga _x In ₁ -xN crystal layer having a multiphase structure by the normal pressure MOCVD method, a preferable growth temperature is in a range of 800 ° C. to 900 ° C.

In order to stably grow a Ga _x In _{1 -x} N crystal layer having a multiphase structure, the growth temperature is controlled within the above range, and ammonia or the like supplied to the reaction furnace with respect to cyclopentadienyl indium. It is also important to adjust the ratio of the raw materials of the group V constituent elements. Ga _x In having a multi-phase structure by atmospheric pressure MOCVD using ammonia as a nitrogen source.
_{In order} to stably form the _1- XN crystal layer, it is preferable that the supply ratio of ammonia to cyclopentadienyl indium is set to about 1.5 × 10 ⁴ or more in terms of mole ratio. Ga _X I by MOCVD
In growing the n ₁ -xN crystal layer, a trialkyl (tri-alkyl) gallium compound such as trimethyl gallium ((CH ₃ ) ₃ Ga) can be used as a gallium (Ga) raw material. The growth rate of the Ga _X In _1-X N crystal layer increases substantially in proportion to the total amount of cyclopentadienyl indium and the gallium (Ga) raw material supplied to the reaction furnace of the MOCVD method, approximately, every second 2Å~ It is desirable that the angle be about 10 ° per second. The preferred growth rate is around 5 ° / sec.

The Ga _x In ₁ -xN having the above-mentioned multiphase structure
In order to grow a crystal layer stably by MOCVD, cyclopentadienyl indium (C
_It is preferable to use ₅ H ₅ In (I)) as an indium raw material and grow while simultaneously adding an organic silicon compound as an impurity. The impurities of the organic silicon compound are Ga _X In _1-X
It has the effect of promoting the generation of N microcrystals. Ga _X In
Fine crystals of _1-X N is a Ga _X In _1-X N crystal layer in the dependent phase. Therefore, while using cyclopentadienyl indium as an indium raw material and simultaneously adding an organic silicon compound as an impurity, Ga _x I
The formation of the n _1-x N crystal layer promotes the generation of a sub-phase composed of microcrystals in the main phase of the Ga _x In _1-x N crystal layer, so that gallium indium nitride having a multiphase structure is efficiently formed. There is an advantage that a crystal layer can be formed. Inorganic silicon compounds, for example, compounds containing a large amount of bonds in which hydrogen (H) atoms and silicon (Si) atoms such as silane (SiH ₄ ) or disilane (Si ₂ H ₆ ) are directly bonded, or halogen (halogen) ) The silicon halide compound containing the element has no effect on the formation of microcrystals (dependent phase) as compared with the case of the organic Si compound. If the silicon impurity added simultaneously with the growth of the Ga _X In _1-X N crystal layer is an inorganic silicon compound or a silicon halide compound as described above, rather than promoting the formation of microcrystals, Ga _X I
Ga _x In _{1-x is formed} by hydrogen or halogen which is desorbed due to thermal decomposition of these impurities during growth of the n _1-x N crystal layer.
The sublimation or etching of the N crystal layer becomes remarkable, and at the same time, the inconvenience of deteriorating the surface state such as impairing the surface smoothness occurs.

Among the alicyclic compounds, cyclopentadienyl indium, preferred organic silicon compounds to be added simultaneously include alicyclic silicon compounds, aromatic silicon compounds and aliphatic silicon compounds. For example, cyclotetramethylenedimethylsilane (composition formula: C ₆ H ₁₄
Si) and alicyclic silicon compounds such as, methyl phenyl silane (formula: and C ₇ H ₁₀ Si) aromatic silicon compounds such as, also, dimethylsilane _{(Si (CH 3) 2 H} 2) and tetraethyl silane ( And aliphatic silicon compounds such as alkyl silanes such as (C ₂ H ₅ ) ₄ Si). On a substrate, cyclopentadienyl indium (C ₅ H ₅ In (I)) having a monovalent valence is used as an indium raw material, and an organic silicon compound is simultaneously added as an impurity while Ga _x In ₁ -xN is added. In the case of forming a crystal layer, the indium raw material and the organic silicon impurity may be independently supplied to a reactor for growth. Alternatively, a predetermined concentration of organic silicon impurities may be contained in the indium raw material in advance and supplied to the reactor for growth. When a predetermined concentration of the organic silicon impurity is previously contained in the indium raw material, the supply amount of the organic silicon impurity to the reaction furnace is increased because the organic silicon impurity is supplied to the reaction furnace simultaneously with the supply of the indium element. Can be formed without the necessity of separately and separately controlling and supplying complicated Ga _x In ₁ -xN crystal layers.

Silicon (Si) is an n-type impurity for Ga _x In ₁ -xN. That is, it is a donor impurity. In the group III nitride semiconductor light emitting device, electrons are transferred to a majority carrier.
In order to preferably utilize the n _-type Ga _x In _1-x N crystal layer as the active layer as the active layer, the organic silicon compound is simultaneously added as an impurity to form the Ga _x In _1-x N crystal layer. When grown, n-type Ga _x is conveniently and stably formed.
There is an effect that an active layer made of In _1-X N is provided.
However, if the concentration of the organic silicon compound is added simultaneously with the cyclopentadienyl indium extremely large, Ga _X In _1-X N crystal layer having poor surface state failure occurs caused. Therefore, the concentration of the organic silicon impurity is set to 100 wt ppm in terms of the concentration of the silicon element with respect to the indium raw material.
In the following case, the deterioration of the surface state can be prevented. On the other hand, if the concentration of the organosilicon compound is excessively low, there is a problem that a microcrystal (dependent phase) is not efficiently generated. The amount of the dependent phase (microcrystal) in the main phase of the Ga _X In _1-X N crystal layer needs to be at least about 1 × 10 ¹² cm ⁻³ . Also, Ga _{x having} a multiphase structure constituting the active layer is used.
The In1 _- XN crystal layer preferably has some conductivity. Therefore, the concentration of the organosilicon compound with respect to the indium raw material is set to 0.1 wt ppm as the concentration of the silicon element.
If above, it is possible to obtain the Ga _X In _1-X N crystal layer exhibiting n-type conductivity carrier concentration exceeds about 1 × 10 ¹⁶ cm ^-3 to ensure, at the same time Ga _X In _1-X N A dependent phase producing a quantum effect can be formed with a density of 1 × 10 ¹² cm ⁻³ or more in the main phase of the crystal layer. That is, the amount of an organosilicon compound suitable for efficiently forming a Ga _x In _1-x N crystal layer having an appropriate number of dependent phases and a carrier concentration, having a multiphase structure, and having an excellent surface state is determined by using an indium raw material. 0.1 to 100 weight parts pp
m. When an organic silicon compound is contained in cyclopentadienyl indium as an impurity in advance, the weight concentration of the silicon element in cyclopentadienyl indium can be determined, for example, by mass spectrometry (MASS), inductively coupled plasma emission spectroscopy ( ICP) method, or an IC that combines them
P-MASS method or atomic absorption spectroscopy (AAS)
It can be quantified by a microanalysis method such as the method.

The multi-phase gallium indium nitride (Ga _X In _{1 -X} N: 0 ≦ X <
1) The crystal layer can be preferably used as an active layer (light emitting layer or well layer) of a group III nitride semiconductor light emitting device such as a light emitting diode (LED) or a laser diode (LD). This is because high-intensity light emission can be obtained by forming a quantum structure convenient for generating low-dimensional carriers such as a quantum box or a quantum dot structure in the active layer. The active layer composed of the gallium indium nitride crystal layer having such a multiphase structure is preferably formed in contact with a group III nitride semiconductor layer such as aluminum nitride gallium formed on the substrate. When a gallium-indium nitride crystal layer is formed in contact with a group III nitride semiconductor layer, it is compared with a case where it is formed directly on a substrate such as sapphire, which is usually used, from the viewpoint of crystal lattice consistency. This is because a gallium-indium nitride crystal layer having a multiphase structure which is advantageous as an active layer and has more excellent crystallinity can be grown. Also,
II such as aluminum nitride and gallium formed on the substrate
A method of forming a gallium-indium nitride crystal layer having a multiphase structure on a group I nitride semiconductor layer at a relatively low temperature, that is, at a temperature equal to or lower than the growth temperature of the group III nitride semiconductor crystal layer, involves sublimation. This is effective in suppressing the volatilization and decomposition of the gallium indium nitride crystal layer, and is therefore effective in forming a gallium indium nitride crystal layer having a desired indium composition ratio with high efficiency.

A high-luminance group III nitride semiconductor light emitting device
Appropriate general processing such as laying n-type and p-type ohmic electrodes on a wafer having a semiconductor layer structure for a light emitting device having an active layer composed of a gallium indium nitride crystal layer formed by the above method is performed. It can be formed by applying. If an n-type or p-type conductive crystal is used as the substrate, an n-type or p-type ohmic electrode can be provided on the back side of the substrate. It is no longer necessary to delete the file, which is convenient.

[0027]

A cyclopentadienyl indium (C ₅ H ₅ In (I)) having a monovalent valence is used as an indium raw material on a substrate, and the concentration of silicon (Si) element with respect to the indium raw material is adjusted. While simultaneously adding 0.1 to 100 ppm by weight of an organic silicon compound as an impurity, gallium indium nitride (Ga _x
In _1-X N: 0 ≦ X <1) By forming a crystal layer, a nitride having a multiphase structure and an excellent surface state having an appropriate number of microcrystals (dependent phases) and a carrier concentration on a substrate. A gallium / indium crystal layer can be efficiently formed. The main phase mainly constituting the crystal layer of the gallium indium nitride crystal layer, and the main phase is formed of indium (I
n) When composed of a multi-phase structure having different composition ratios and a subphase mainly composed of microcrystals, the subphases composed of microcrystals generate low-dimensional carriers such as quantum boxes or quantum dot structures. To form a convenient quantum structure. The active layer composed of the gallium indium nitride crystal layer having the above-described quantum structure can provide high-intensity light emission. Therefore, the multi-phase gallium indium nitride (Ga _X In _{1 -X)} N: 0 ≦ X <1) The crystal layer can be preferably used as an active layer (light emitting layer or well layer) of a group III nitride semiconductor light emitting device such as a light emitting diode (LED) or a laser diode (LD).

Further, the gallium-indium nitride crystal layer is
When formed on a Group III nitride semiconductor layer, the lattice constant of the gallium-indium nitride crystal layer and the underlying crystal is lower than when formed directly on a substrate such as sapphire, which is commonly used. Is small, a gallium-indium nitride crystal layer having a multiphase structure, which is advantageous as an active layer and has more excellent crystallinity, can be grown from the viewpoint of crystal lattice matching.

[0029]

EXAMPLES (Example 1) Hereinafter, the content of the present invention will be specifically described by taking an example of manufacturing an LED. Example 1
FIG. 1 schematically shows a planar structure of an LED 1A manufactured from the wafer described in FIG. FIG. 2 is a broken line AA ′ of FIG.
It is a schematic diagram which shows the cross-sectional structure of the center part of LED1A which followed. When a wafer having a semiconductor layer structure for the LED is formed, each semiconductor layer is subjected to a normal pressure (substantially atmospheric pressure) MOC.
Grown by VD method.

The wafer manufactured in the first embodiment has sapphire (α-Al ₂ O ₃ single crystal) as the substrate 101. On the (0001) surface of the sapphire substrate 101, a buffer layer 102 made of undoped GaN was deposited using trimethylgallium ((CH ₃ ) ₃ Ga) and liquefied ammonia as raw materials. The GaN buffer layer 102 was grown at a growth temperature of 430 ° C. and a ratio of group V source to group III source of 1.6 × 10 ⁴ . As a result, a buffer layer 102 mainly composed of a single crystal was formed in a region near the bonding interface with the sapphire substrate 101. The upper region of the buffer layer 102 having a layer thickness of about 17 nm
It was mainly an amorphous region.

On the buffer layer 102, a carrier concentration of about 3
An undoped GaN layer of × 10 ¹⁷ cm ⁻³ was deposited as the first constituent layer 103 a of the n-type cladding layer 103.
The first constituent layer 103a was grown at 1050 ° C., and the thickness was 0.8 μm.

On the first constituent layer 103a, 10
At 50 ° C., the second constituent layer 103b of the n-type cladding layer is doped with Si and has a carrier concentration of about 4 × 10
An n-type GaN layer of ¹⁸ cm ^-3 was laminated. The layer thickness of the second constituent layer 103b doped with Si was set to about 2.5 μm.

[0033] Then, on the second constituent layer 103b, at 1050 ° C., and depositing a high carrier concentration layer 103c made of GaN having a carrier concentration of about 8 × 10 ¹⁹ cm ^-3 doping of Si. High carrier concentration 103c
Was about 1.5 nm. The above three layers 103
The n-type cladding layer 103 was composed of a, 103b, and 103c.

890 ° C. on the n-type cladding layer 103
Then, using a cyclopentadienyl indium containing an alicyclic compound of silicon (Si) as a main silicon impurity as an indium raw material, a Ga _0.88 In _0.12 N crystal layer having an average composition of indium of _0.12. The n-type active layer 104 made of was formed. Frameless (frame-
Less) As a result of measurement using atomic absorption spectrometry, the concentration of the organic silicon compound in the indium raw material was determined to be approximately 23 ppm by weight in terms of the concentration of silicon (Si) element relative to the indium raw material. . The alicyclic compound of silicon (Si) as an impurity was considered to be mainly composed of cyclotetramethylenedimethylsilane as a result of measurement by infrared absorption spectroscopy. In growing the n-type active layer 104, ammonia (NH ₃ ) was used as a nitrogen source, and the supply ratio of NH _{3 to} cyclopentadienyl indium was set to 3.4 × 10 ⁴ . The growth rate is normal pressure M
The total supply amount of cyclopentadienyl indium and trimethylgallium ((CH ₃ ) ₃ Ga) as a raw material of gallium (Ga) to the reactor of the OCVD method was adjusted to about 4
Å / sec. The carrier concentration of the active layer 104 is about 4 × 1
0 ¹⁷ cm ^-3 . The thickness of the main phase of the grown Ga _0.88 In _0.12 N crystal layer is about 6 nm, and the thickness of the main phase S is n.
The thickness is substantially equal to the thickness of the active layer 104.

On the n-type active layer 104, at 1100.degree.
A cladding layer 105 was formed. This p-type cladding layer 1
Reference numeral 05 denotes Mg in which the Al composition is reduced linearly in the p-type cladding layer 105 so that the Al composition is 0.15 at the bonding interface with the n-type active layer 104 and the Al composition is 0 at the surface.
Doped p-type Al _x Ga ₁ -xN crystal layer (X = 0.1
5 → 0, layer thickness = 120 nm, carrier concentration = 2 × 10 ¹⁷
cm ^-3 ). When the growth of the p-type cladding layer 105 was completed, the formation of the LED wafer of Example 1 was completed.

After forming a wafer having a semiconductor layer structure for an LED as described above, a _subphase having a substantially uniform diameter is generated in the Ga _0.88 In _0.12 N crystal layer of the n-type active layer 104. The wafer was then cooled from 1100 ° C to 950 ° C at a rate of 50 ° C per minute. In addition, 95
The temperature was lowered from 0 ° C. to 650 ° C. at a cooling rate of 10 ° C./min for 20 minutes. FIG. 3 is a schematic view of a cross-sectional TEM image when the internal crystal structure of the n-type active layer 104 after the above cooling is observed by a transmission electron microscope (TEM). The Ga _0.88 In _0.12 N crystal layer of the n-type active layer 104 is made of Ga _0.94 In _0.06 N having an indium composition ratio of about 0.06, which mainly forms the crystal layer.
Has a multi-phase structure composed of a main phase S composed of a main phase S and a subphase T mainly composed of substantially spherical microcrystals having an average diameter of about 4 nm and having a different indium composition ratio. Was. The existence of the strain layer U having a thickness of about 1 nm was generally found around the dependent phase T. The thickness of the strained layer U was generally uniform to about 25% of the diameter of the dependent phase T. Also,
The density of the dependent phase T existing inside the main phase S is determined by the sectional TE
It was about 2 × 10 ¹⁶ cm ⁻³ when calculated based on the average number of the dependent phases T existing in the imaging range of the M image.

A patterning technique based on a general photolithography technique and argon (A)
r) / Processing for forming an element (chip) using a plasma etching technique using a mixed gas of methane (CH ₄ ) / hydrogen (H ₂ ), etc., to produce a substantially square LED 1A having a side of about 320 μm. did. The side of the p-type ohmic electrode 106 of the LED 1A which is in contact with the surface of the p-type cladding layer 105 composed of the Mg-doped Al _x Ga ₁ -xN composition gradient layer is made of a gold-zinc alloy (Au 95% by weight, Zn 5% by weight). Pedestal electrode 1 having a two-layer structure in which the upper layer is made of gold (Au)
06a and a translucent electrode 106b formed of a multilayer thin film of Au and nickel oxide (NiO). The n-type ohmic electrode 107 was placed in contact with the second constituent layer 103b of the lower clad layer 103 whose upper portion was removed by plasma etching and exposed. The n-type ohmic electrode 107 was made of aluminum (Al).

The forward current of 20 mA is applied between the p-type ohmic electrode 106 and the n-type ohmic electrode 107 of the LED 1A.
, And blue light emission having a central emission wavelength of 460 nm was obtained. The main emission spectrum of this emission does not show the appearance of an accompanying subordinate spectrum,
Therefore, the half width of the emission spectrum was as good as about 11 nm. In addition, the light emitting region of the LED 1A spread over substantially the entire surface of the active layer 104 having a plane area of about 4 × 10 ⁻⁴ cm ⁻² after the above-mentioned etching process. Thus, the light emission intensity of the LED measured by a general integrating sphere is as excellent as about 22 microwatts (μW) in a chip state, and a high-luminance group III nitride semiconductor light emitting device is formed. It became.

(Embodiment 2) In this embodiment 2, MOCVD
The content of the present invention will be specifically described by taking an example of manufacturing another LED by the method. FIG. 4 schematically shows a cross-sectional structure of the LED 2A formed in the second embodiment. First, Example 1
Similarly, the buffer layer 102 is formed on the sapphire substrate 101.
And three layers 103a, 103b,
An n-type cladding layer 103 of 103c was formed. Thereafter, on the n-type cladding layer 103, an n-type G
The barrier layer 108 made of aN and the well layer 109 made of n-type Ga _0.90 In _0.10 N having an average indium composition ratio of 0.10 are alternately and repeatedly stacked to form a multiple quantum well (MQW) having five periods. ) An n-type active layer 104 having a structure was formed.

The barrier layer 108 and the well layer 109 are both 87
Formed at 0 ° C. The GaN barrier layer 108 was formed from an n-type low-resistance layer doped with Si so that the carrier concentration became about 2 × 10 ¹⁸ cm ⁻³ and having a thickness of about 30 nm. The well layer 109 is formed by using, as an indium raw material, cyclopentadienylindium containing an alicyclic silicon compound or an aromatic silicon compound as a main silicon impurity and containing the organic silicon impurity at a concentration of 86 wt ppm of a silicon element with respect to the indium raw material. did. The impurity alicyclic silicon compound or aromatic silicon compound was considered to consist mainly of methylphenylsilanes as a result of measurement by infrared absorption spectroscopy. During the growth of the well layer 109 by the MOCVD method, the temperature of the indium raw material was kept at a constant temperature of 65 ° C. The supply ratio of ammonia as the nitrogen source to the indium source to the reactor in the atmospheric pressure MOCVD method is 2 × 10
Set to ⁴ . The layer thickness of the well layer 109 was 5 nm.

The same p-type cladding layer 10 as in the first embodiment is provided on the well layer 109 which terminates the n-type active layer having the MQW structure.
5 was formed at 1100 ° C. After the formation of the p-type cladding layer 105 is completed, the produced wafer is heated to 950 ° C. for 75 minutes per minute.
Cooled at a rate of ° C. Further, the temperature was lowered to 650 ° C. at a cooling rate of 15 ° C./min. By this cooling operation, the active layer 104 was more reliably formed into a multiphase structure. As a result of observing the internal structure of the crystal of the active layer by a transmission electron microscope, for example, MQ
In the well layer 109 at the end of the W structure, Ga _0.90 In _0.10 N
The crystal layer had a multiphase structure. In addition, the diameter of the dependent phase composed of substantially spherical microcrystals in the main phase was about 3 nm, and the density was measured to be about 4 × 10 ¹⁶ cm ⁻³ . The thickness of the strained layer around the microcrystal forming the subphase is generally about 1 nm, and is about 30 nm of the diameter of the microcrystal.
%.

The wafer fabricated as described above is processed in the same manner as in Example 1 to obtain an LE having a quantum well structure active layer.
D2A was produced. Approximately 3. forward between the electrodes of the LED.
When a voltage of 8 V is applied and a forward current of 20 mA flows, the blue emission spectrum has a center emission wavelength of about 465 nm.
And the half width was about 9 nm. The light emission output of the LED in a chip state measured by a general integrating sphere method is 26.
μW, and a high-luminance group III nitride semiconductor light emitting device was obtained.

[0043]

According to the vapor phase growth method of a gallium indium nitride crystal layer of the present invention, a gallium indium nitride crystal layer having a multiphase structure containing a microcrystal which can function as a quantum box or a quantum dot as a dependent phase is obtained. Since the wafer can be formed efficiently, a high-intensity Group III nitride semiconductor light emitting device can be obtained from a wafer including the layer as an active layer. In the above description, the case where the gallium indium nitride crystal layer according to the present invention is used as an active layer of a group III nitride semiconductor light emitting device has been described as an example. The indium crystal layer can be suitably used for manufacturing another group III nitride semiconductor device using a quantum structure such as a quantum box or a quantum dot that provides low-dimensional carriers.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of an LED according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the LED along AA ′ of FIG.

FIG. 3 is a schematic diagram of a cross-sectional TEM image of an internal crystal structure of an n-type active layer 104 of Example 1.

FIG. 4 is a schematic sectional view of an LED according to a second embodiment of the present invention.

FIG. 5 is a view schematically showing a reaction furnace for growing a crystal layer by an atmospheric pressure MOCVD method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Cyclopentadienyl indium 10a 1st storage container which stores cyclopentadienyl indium 10b 2nd storage container which stores cyclopentadienyl indium 20 MOCVD reactor 21 Gas introduction hole 22 Susceptor 23 Substrate 24 Heating body 25 Partition wall 26 Distance between partition wall and substrate 27 Susceptor vertical mechanism 30 Reaction region 1A, 2A LED 101 Substrate 102 Buffer layer 103 N-type cladding layer 103a First component layer of n-type cladding layer 103b Second configuration of n-type cladding layer Layer 103c high carrier concentration layer 104 n-type active layer 105 p-type cladding layer 106 p-type ohmic electrode 106a pedestal electrode 106b translucent electrode 107 n-type ohmic electrode 108 barrier layer 109 well layer S main phase T dependent phase U strained layer

Claims (3)

[Claims] In a vapor phase growth method of a gallium indium nitride crystal layer by a metalorganic thermal decomposition vapor phase growth method, cyclopentadienyl indium (C ₅ H ₅ In () having a monovalent valence is formed on a substrate. I)) is used as an indium raw material, and at the same time, an organic silicon compound having a concentration of silicon (Si) element of 0.1 to 100 ppm by weight based on the indium raw material is added as an impurity while organic metal pyrolysis vapor phase growth is performed. Gallium indium nitride (Ga _X In _1-X
N: 0 ≦ X <1) A vapor phase growth method for a gallium indium nitride crystal layer, comprising forming a crystal layer. 2. The gallium-indium nitride crystal layer is composed of a main phase mainly constituting the crystal layer and a sub phase mainly composed of microcrystals having a different indium (In) composition ratio from the main phase. The method for growing a gallium indium nitride crystal layer according to claim 1, wherein the method has a multiphase structure. 3. The gallium nitride nitride film according to claim 1, wherein the gallium indium nitride crystal layer is formed in contact with a group III nitride semiconductor layer formed on the substrate. A vapor phase growth method for an indium crystal layer.