JPH05243153A - Growth of semiconductor thin film - Google Patents

Abstract

PURPOSE:To obtain a gallium nitride semiconductor thin film, which is superior in surface smoothness and crystallinity, by a method wherein the interior of a thin film growing chamber is held in a high vacuum, the partial pressure of a carbon-containing compound is specified and ammonia gas or nitrogen trifluoride is fed as a nitrogen source. CONSTITUTION:A substrate 8 is heated to 1000 deg.C or higher and is set on a substrate heating holder in a vacuum container. Evaporation crucibles 2 with Ga put therein are heated and treated at 1000 deg.C or higher, whereby a degassing is previously performed and the partial pressure of carbon-containing impurities in the vacuum container is held at 10<78>Torr. In the introduction of ammonia gas or nitrogen trifluoride which is used as a nitrogen source, a cracking gas cell 6 whose inside is filled with alumina fibers is used, is heated to 600 deg.C and the gas is directly blown to the substrate 8. Thereby, a gallium nitride semiconductor thin film, which is superior in surface flatness and crystallinity, can be obtained.

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 a gallium nitride-based semiconductor thin film which can be used in, for example, a light emitting diode in the ultraviolet range to orange, which is most suitable for displays and optical communications, and a laser diode.

[0002]

2. Description of the Related Art Semiconductor devices, particularly visible light emitting diodes (LEDs), have been used as display devices in a wide range of fields, but conventionally, ultraviolet to blue light emitting diodes and laser diodes have not been put into practical use. In particular, development is urgently needed for displays that require three primary colors. It has been reported that ZnSe, ZnS, GaN, SiC and the like are used as light emitting diodes and laser diodes in the ultraviolet range to blue.

Most gallium nitride-based semiconductor thin films are formed on the sapphire C surface by MOCVD or VPE. [Journal of Appli]
edPhysics, 56 P.D. 2367-2368
(1984)], it was necessary to raise the reaction temperature, which was not only difficult to manufacture, but also the carrier density was extremely high due to lack of nitrogen, and it was difficult to obtain a thin film having good semiconductor characteristics. A method based on the gas source MBE method is also used [Journalof Ap.
plied Physics, 42 P.P. 427-42
9 (1983)], the current situation is that no gallium nitride based semiconductor thin film applicable to a light emitting device has been obtained yet.

In the GaInN mixed crystal semiconductor thin film, the film is formed on the sapphire C surface by the MOCVD method or the VPE method. [Journal of Applied]
Physics, 28 L-1334 (198)
9)], it is difficult to obtain a good quality GaInN mixed crystal semiconductor thin film because the growth temperatures of GaN and InN are largely different. As for the GaAlN mixed crystal semiconductor thin film, an example in which it is formed by a gas source MBE method using ammonia gas is reported [Journal of Appli.
ed Physics, 53 (1982) 6844-.
6848], although cathodoluminescence is observed at the temperature of liquid nitrogen, a high-quality semiconductor capable of producing a light emitting device has not yet been obtained.

In addition, control of the atmosphere during the growth of the gallium nitride based semiconductor thin film has not been studied so far, and the effect of the growth atmosphere on the characteristics of the gallium nitride based semiconductor thin film has not been clearly understood. The current situation. Furthermore, when using a method such as MOCVD or VPE,
Since it is necessary to use a raw material containing carbon and the pressure during film formation is relatively high, a large amount of carbon and oxygen are incorporated as impurities in the thin film, and only gallium nitride-based semiconductor thin films with low characteristics can be obtained. There was a problem that it did not exist.

[0006]

In order to produce a gallium nitride-based thin film having excellent characteristics as a semiconductor thin film, it is necessary but not realized to reduce the impurity concentration of carbon and oxygen in the thin film. is the current situation. The present invention is
An object of the present invention is to solve this problem and manufacture a gallium nitride based semiconductor thin film having good characteristics as a semiconductor.

[0007]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a method for producing a gallium nitride based semiconductor thin film by a film formation method in which the atmosphere during film formation is controlled. Came to According to the present invention, in the production of a gallium nitride-based semiconductor thin film, the thin film growth chamber is kept in a high vacuum, the partial pressure of the carbon-containing compound is maintained at 10 ⁻⁸ Torr or less, and ammonia gas or nitrogen trifluoride is supplied as a nitrogen source. And a method for growing a gallium nitride based semiconductor thin film.

The high vacuum in the present invention means 10 ^-5 Torr
The pressure below is the pressure of 10 ^-5 Torr or less and the mean free path is increased so that the gases and metal vapors necessary for growth of the gallium nitride based semiconductor thin film reach the substrate without colliding with each other. Is preferable, and the gas source MBE method is the most preferable growth method. In the present invention, by reducing the concentration of the carbon-containing compound in the growth chamber when producing a gallium nitride-based thin film as much as possible,
It is important to reduce the impurities of carbon and oxygen in the obtained thin film, and it is necessary to adjust the carbon-containing impurities to a partial pressure of 10 ^-8 Torr or less. The types of carbon-containing impurities are mainly carbon monoxide, carbon dioxide and methane,
Sometimes there are high molecular weight hydrocarbons and organometallic compounds. Among these, it is particularly important to control the partial pressures of carbon monoxide and carbon dioxide, and if these partial pressures are made small, the impurity concentrations of carbon and oxygen taken into the gallium nitride-based semiconductor thin film also become small. Therefore, the partial pressure of carbon monoxide or carbon dioxide is more preferably 10 ⁻¹⁰ Torr or less. The type and partial pressure of impurities in the growth chamber can be measured by a quadrupole mass spectrometer.

Impurities in the growth chamber are considered to come out from various parts constituting the vacuum container, raw materials to be supplied, and the like. In order to remove these, a method of baking the vacuum container for a long time, a solid to be supplied. A method of degassing by heating the raw material in a vacuum vessel, a method of cleaning ammonia gas or nitrogen trifluoride introduced into the vacuum vessel with an adsorbent in advance, selection of the material and raw material used, There are means for exhausting or trapping the generated carbon-containing compound, and by appropriately combining these, it becomes possible to create a growth atmosphere with a low carbon-containing compound.

As a method of controlling the atmosphere, the vacuum container is 10
A preferable method is to perform baking for a long time at a temperature of 0 ° C. or higher and to perform sufficient degassing treatment. The baking temperature may be set within a range where the vapor pressure of the supplied metal is sufficiently small, and in consideration of the heat resistance of the vacuum container and the components forming the vacuum container. The temperature is preferably 150 ° C or higher, more preferably 180 ° C or higher. Is to be done in. The longer the baking time, the better the removal of impurities,
In consideration of the baking temperature, it is practically 24 hours or longer, preferably 48 hours or longer. Further, it is preferable that the gas line for supplying the ammonia gas or the nitrogen trifluoride into the vacuum container is as short as possible and baking is performed as described above. Further, it is preferable not only to select a solid material having a high purity as the solid material to be supplied but also to perform heating at a temperature of several tens of degrees higher than the heating temperature at the time of growth after being introduced into the vacuum vessel.

As the nitrogen source in the present invention, ammonia gas, nitrogen trifluoride, or a mixed gas mainly containing ammonia gas or nitrogen trifluoride can be used. As a gas mixed with ammonia gas or nitrogen trifluoride, an inert gas such as nitrogen, argon or helium is used. The supply amount of ammonia gas or nitrogen trifluoride needs to be larger than the supply amount of Ga on the substrate surface.
The supply amount of ammonia gas or nitrogen trifluoride is Ga, In,
Alternatively, if the supplied amount of the group III element such as Al is smaller than the supplied amount, nitrogen is more likely to escape from the gallium nitride-based semiconductor thin film that is produced, so that a good gallium nitride-based semiconductor thin film cannot be obtained. Therefore, the supply amount of ammonia gas or nitrogen trifluoride is 10 times or more, preferably 100 times or more, more preferably 10 times that of the group III element.
It is to make it 00 times or more.

A gas cell may be used as a method for supplying ammonia gas or nitrogen trifluoride.
Alumina, quartz, stainless steel, etc. tubes are installed in the thin film growth device with the opening facing the substrate surface, and the valve, flow rate control device, and pressure control device are connected to control the supply amount and start and stop the supply. It's something you can do.

It is also preferable to use a cracking gas cell because it decomposes ammonia gas or nitrogen trifluoride to efficiently supply active nitrogen to the substrate surface. The cracking gas cell is one that heats ammonia gas or nitrogen trifluoride in the presence of a catalyst to efficiently generate active nitrogen, and the catalyst is a ceramic such as alumina, silica, boron nitride, or silicon carbide. It is preferable to increase the surface area by making it fibrous or porous. The cracking temperature varies depending on the type of catalyst, the supply amount of a nitrogen source such as ammonia gas and nitrogen trifluoride, etc., but is preferably set in the range of 100 to 700 ° C.

As the substrate used in the present invention, generally used glass, polycrystalline substrate, or single crystal substrate can be used. Examples thereof include quartz glass, glasses such as high silicate glass, GaAs, InAs,
III-V group compound semiconductors such as InP, II-VI group compound semiconductors such as ZnSe, Si, Ge, SiC
Substrate such as AlN, ZnO, MgO, A
There are single crystal substrates made of l ₂ O ₃ , ZnO, TiO ₂ , ZrO _2, etc.

Further, an amorphous substance such as AlN, GaN, Si, or SiC is used as a buffer layer between the above substrate and the gallium nitride based semiconductor thin film to be grown.
Etc., or as a single crystal substance, for example, AlN, Zn
O, SiC, etc. can be provided. Among them, in the single crystal substrate as described above, an integer multiple of at least one lattice constant of the gallium nitride based semiconductor thin film formed on the substrate is 5% or less, preferably an integer multiple of the lattice constant of the single crystal substrate. It is preferable to use a single crystal substrate having a crystal surface that causes a mismatch of 2% or less.
As a method of obtaining a substrate having such a crystal surface,
This can be carried out by growing a crystal so that a plane inclined by a desired angle from the appropriate surface of the single crystal substrate as a reference, or by growing and then cutting and polishing. In addition, commonly used glass,
On a polycrystalline substrate or a single crystal substrate, a single crystal or highly oriented crystal in which the integer multiple of the lattice constant of the gallium nitride-based semiconductor is mismatched with the integer multiple of the lattice constant of the single crystal substrate by 5% or less. A thin film can be formed and a desired gallium nitride based semiconductor thin film can be grown on it.

As the single crystal substrate, it is particularly preferable to use an R-plane substrate of sapphire (Al ₂ O ₃ ), and its off angle is preferably 0.8 degrees or less.
Furthermore, it is more preferable to use a surface obtained by rotating the sapphire R surface by 9.2 degrees about the R surface projection of the sapphire c-axis, and it is possible to obtain a gallium nitride based semiconductor thin film having excellent characteristics. The substrate is 2 by the substrate heating device.
Heat in the range of 00 to 900 ° C.

The gallium nitride based semiconductor thin film in the present invention means, for example, Ga _{1 -x} Al _x N, Ga _{1 -x in} addition to GaN.
In _x N, Ga _1-xy In _x Al _y , NGa _1-x B _x N
Is a mixed crystal compound thin film mainly composed of GaN.
Further, when a gallium nitride-based semiconductor thin film is manufactured, impurities can be doped to perform carrier density control and p-type, i-type or n-type control. Examples of impurities to be doped are Mg, Zn, Be, Cd, Ca, Hg, Li, etc. as p-type or i-type dopants, and Si, Ge, C, Sn, S as n-type dopants.
e, Te, etc. The type of carrier and the carrier density can be changed by changing the type and doping amount of these dopants. Further, it is possible to adopt a structure in which the doping concentration is changed depending on the direction of the film thickness, or a structure in which a δ-doping layer for doping only a specific layer is provided.

In practice, when a gallium nitride based semiconductor thin film is used to manufacture a semiconductor component, particularly a light emitting device (LED), a laser diode, or an electronic device, a mixed crystal of these gallium nitride based semiconductor thin films, p-type or i-type. Type or n-type doped gallium nitride based semiconductor thin films are combined to form a pn junction, pin structure, ppn structure, pn
It is possible to manufacture an element having an n structure, and further a single hetero structure, a double hetero structure, a quantum well structure, a superlattice structure, or the like.

A method for manufacturing a gallium nitride based semiconductor thin film using the gas source MBE method will be described below as an example, but the method is not particularly limited to this. As an apparatus, in a vacuum container 1 as shown in FIG. 1, an evaporation crucible (Knudsen cell) 2, 3, 4, 5 a and 5 b,
Cracking gas cell 6, substrate heating holder 7, quadrupole mass spectrometer 9, RHEED (Refractive H)
IG Energy Diffraction) Gun 1
Gas source MBE equipment with 0 and RHEED screen 11 was used.

Ga metal was put in the evaporation crucible 2 and the Ga beam was 10 ¹³ to 10 ¹⁹ atoms / cm ² ·.
It was heated to a temperature of sec. A cracking gas cell 6 was used to introduce ammonia gas or nitrogen trifluoride, and the ammonia gas or nitrogen trifluoride was installed so as to be directly sprayed onto the substrate 8. The amount introduced is 10 ¹⁶ to 10 on the substrate surface.
^It was supplied so as to have ²⁰ molecules / cm ² · sec. In, Al, etc. are put into the evaporation crucibles 3 and 4, and the temperature is controlled so that a compound semiconductor having a predetermined composition is obtained, and thin film growth is performed. Mg, Ca, Zn, B are used for the evaporation crucible 5
A p-type dopant such as e, Cd, Sr, Hg, and Li is added to the evaporation crucible 5n by n such as Si, Ge, C, Se, and Te.
Doping is performed by adding a type dopant and controlling the temperature and the supply time so that a predetermined supply amount is obtained.

First, the vacuum container is baked at a temperature of 150 ° C. or higher for a long time to sufficiently perform degassing. As the substrate 8, a sapphire R surface having an off angle of 0.8 degrees or less, or a substrate in which the sapphire R surface is rotated by 9.2 degrees about the R surface projection of the sapphire c axis is heat-treated in advance at a predetermined temperature. I used one.

First, the substrate 8 is heated at 900 ° C. in a vacuum container.
After heating, set it to the desired growth temperature and evaporate the crucible.
2 is heated in the vacuum container 1 to perform degassing, and
Set the growth temperature and grow at a growth rate of 0.1 to 30Å / sec.
A GaN thin film having a thickness of 0.05 to 10 μm is produced. Success
Measurement of carbon-containing impurities in the film by quadrupole mass spectrometer 9
And the carbon monoxide was 2 × 10^-9Dioxide at Torr
5 × 10 carbon^{ー 11}It was Torr. This GaN thin film
Carrier density was measured by the Van der Pauw method
Where 10 ¹⁶/ Cm³-10²⁰/ Cm³Met. Well
Also, the photoluminescence was measured at 77K.
, Has a peak near 3.5 eV as shown in FIG.
A spectrum was obtained.

Further, the carbon monoxide content is 1 × 10 ^-11 Tor.
In r, and carrier density of the GaN films grown carbon dioxide under the conditions of 3 × 10 ^{over 1} 1 Torr is 10 ¹⁵ / cm ³
Was ~10 ¹⁸ / cm ^3, was measured photoluminescence at 300K, the spectrum having a peak near 3.4eV was obtained.

[0024]

EXAMPLES The present invention will be described in more detail below with reference to examples.

[0025]

Example 1 Gas source MBE using ammonia gas
An example of growing a GaN thin film on a sapphire substrate by the method will be described. In a vacuum container 1 as shown in FIG.
A gas source MBE equipped with an evaporation crucible 2, a cracking gas cell 6, and a substrate heating holder 7 was used as an apparatus.

First, the substrate 8 is heat-treated at 1100 ° C. for 15 minutes and set in a substrate heating holder in a vacuum container. The evaporating crucible 2 containing Ga was degassed in advance by performing a heat treatment at 1150 ° C. for 1 hour. When the carbon-containing impurities in the vacuum container were measured by a quadrupole mass spectrometer 9, carbon monoxide was found to be 2 × 10 ⁻⁹ To.
The carbon dioxide was 5 × 10 ^-11 Torr at rr.

As the substrate 8, a sapphire R surface having a size of 20 mm square and an off angle of 0.8 degrees or less is used. After that, the substrate temperature is 700 ° C. and the evaporation crucible 2 is 1020 ° C.
Heated to. A cracking gas cell 6 having alumina fibers filled therein was used to introduce the ammonia gas, heated to 600 ° C., and supplied at a rate of 5 cc / min so that the gas was directly blown onto the substrate 8. The film formation rate is 1.0 Å / sec, and the Ga of 0.8 μm is formed.
An N thin film was prepared.

The pressure in the vacuum container is 2 × during film formation.
It was 10 ⁻⁶ Torr. RHEED of this GaN thin film
When a pattern (electron beam incident parallel to the a-axis direction of GaN) was observed, a streak pattern was observed as shown in FIG. 2, and it was found that the surface flatness and crystallinity were good. From a surface photograph by an electron microscope, it was found that the surface was flat. Further, the carrier density was measured by the Van der Pauw method to be 4 × 10 ¹⁸ / cm ^3.
When the photoluminescence was measured at 77 K, a spectrum having a peak near 3.5 eV was obtained as shown in FIG.

[0029]

[Comparative Example 1] Carbon-containing impurities during film formation, carbon monoxide carbon dioxide at 2 × 10 ^-8 Torr 7 × 10 ^{over 10} Tor
A GaN thin film with a film thickness of 0.8 μm was grown by the same method as in Example 1 except that r was r. Observation of the RHEED pattern (electron beam incident parallel to the a-axis direction of GaN) of this GaN thin film revealed a random spot-shaped pattern as shown in FIG. 3, which resulted in deterioration of surface flatness and crystallinity. I found out. From the surface photograph by electron microscope, it was found that the surface was rough.

In addition, the carrier density is determined by the van der por
3 × 10 when measured by the method ¹⁹/ Cm³And
It was Photoluminescence measured at 77K
The strength is small around 2.5eV as shown in Fig. 5.
A spectrum with broad peaks was obtained. This is charcoal
Elemental and oxygen are taken into the GaN thin film as impurities.
Impurity level is generated by the
Considered to be light.

[0031]

[Example 2] Gas source MBE using ammonia gas
An example in which a Ga _1-x In _x N mixed crystal thin film is grown by the method will be described. A gas source MBE provided with an evaporation crucible 2 and 3, a cracking gas cell 6, and a substrate heating holder 7 was used as an apparatus in a vacuum container 1 as shown in FIG.

First, the substrate 8 is heated at 1100 ° C. for 15 minutes and set in a substrate heating holder in a vacuum container. Further, the evaporation crucible 2 containing Ga is set to 1150.
The vaporizing crucible 3 containing In was heated at 800 ° C. for 1 hour at 800 ° C. to degas in advance. Was measured by the quadrupole mass spectrometer 9 carbon-containing impurities in the vacuum chamber, carbon monoxide 3 × 10 ^-9 Torr, carbon dioxide 6 × 10 ^{over 11} Torr, methane 1 × 10 ^-11 Tor
It was r.

As the substrate 8, a sapphire R surface having a size of 20 mm square and an off angle of 0.8 degrees or less is used. Then, the substrate temperature is set to 700 ° C., and the evaporation crucible 2 is set to 1020.
C., the evaporation crucible 3 was heated to 660.degree. A cracking gas cell 6 having alumina fibers filled therein is used to introduce ammonia gas, and heated to 600 ° C.,
Gas is sprayed directly onto the substrate 7 so that 10 cc /
It was supplied at a rate of min. The shutters of the evaporation crucibles 2 and 3 were opened, and a Ga _1-x In _x N mixed crystal thin film (x = 0.2) having a film thickness of 0.8 μm at a film forming rate of 1.2Å / sec.
To make.

The pressure in the vacuum container is 2 × during film formation.
It was 10 ⁻⁶ Torr. When the RHEED pattern of this mixed crystal thin film was observed, a streak pattern was observed, and it was found that the surface flatness and crystallinity were good.
The carrier density of this mixed crystal thin film was 2 × 10 ¹⁸ / cm ^{3 as} measured by the Van der Pauw method. When photoluminescence was measured at 77 K, a spectrum having a peak near 2.9 eV was obtained.

[0035]

[Example 3] Gas source MBE using ammonia gas
GaN MIS (Metal / Insula)
An example of producing a tor / Semiconductor type structure will be described. The apparatus uses a gas source MBE equipped with an evaporation crucible 2, an evaporation crucible 5a, a cracking gas cell 6, and a substrate heating holder 7 in a vacuum container 1 as shown in FIG.

First, the substrate 8 is heat-treated at 1100 ° C. for 15 minutes and set in a substrate heating holder in a vacuum container. The evaporation crucible 2 containing Ga was heated at 1150 ° C.
The evaporation crucible 5 containing g was heated at 400 ° C. for 1 hour to degas in advance. When the carbon-containing impurities in the vacuum container were measured by the quadrupole mass spectrometer 9, carbon monoxide was 1 × 10 ⁻⁹ Torr and carbon dioxide was 4
× 10 ^{over 11} Torr, methane was 2 × 10 ^-11 Torr.

As the substrate 8, a surface obtained by rotating a sapphire R surface having a size of 20 mm square by 9.2 degrees about the R surface projection of the sapphire axis as a rotation axis is used. Then, the substrate temperature was heated to 700 ° C., the evaporation crucible 2 was heated to 1020 ° C., and the evaporation crucible 4 was heated to 290 ° C. A cracking gas cell 6 having alumina fibers filled therein was used to introduce the ammonia gas, and the ammonia gas was heated to 600 ° C. so that the gas was directly blown onto the substrate 8 and supplied at a rate of 7 cc / min. First, open the shutter of the Ga evaporation crucible,
N- with a film thickness of 1.0 μm at a film forming rate of 1.5 Å / sec
A GaN thin film is prepared. Then, the shutters of the Ga vaporizing crucible 2 and the magnesium vaporizing crucible 5 are simultaneously opened, and the film thickness is set to 50 Å / sec.
GaNMI is formed by forming a 0Å doping layer.
A laminated film having an S structure was produced.

When the RHEED pattern of this GaN laminated thin film was observed, a streak pattern was observed, and it was found that the surface flatness and crystallinity were good. Further, the photoluminescence of this GaN laminated thin film at 77 K was measured, and a spectrum having a peak near 3.5 eV was obtained. In addition, GaN that is insulative with the n-GaN layer
An Al electrode was formed on each of the layers by vacuum vapor deposition to obtain a MIS type device having a structure as shown in FIG. That current −
When the voltage characteristic was measured, the diode characteristic as shown in FIG. 7 was obtained.

[0039]

Example 4 Gas source MBE using ammonia gas
An example of growing a GaN thin film on a sapphire substrate by the method will be described. First, the vacuum container 1 and the gas line for introducing ammonia are baked at 180 ° C. for 100 hours. The substrate 8 is heat-treated at 1100 ° C. for 15 minutes and set in a substrate heating holder in a vacuum container. Further, the evaporation crucible 2 containing Ga was heated at 1150 ° C. for 3 hours to degas in advance. Was measured by the quadrupole mass spectrometer 9 carbon-containing impurities in the vacuum container, carbon monoxide 1 × 10 ^-11 Torr, carbon dioxide 3 × 10 ^{over 11} Torr, carbon-containing compounds such as methane to detect I couldn't.

As the substrate 8, a sapphire R surface having a size of 20 mm square and an off angle of 0.8 degrees or less is used. After that, the substrate temperature is 700 ° C. and the evaporation crucible 2 is 1020 ° C.
Heated to. A cracking gas cell 6 having alumina fibers filled therein was used to introduce the ammonia gas, heated to 600 ° C., and supplied at a rate of 5 cc / min so that the gas was directly blown onto the substrate 8. The film formation rate is 1.0 Å / sec, and the Ga of 0.8 μm is formed.
An N thin film was prepared.

The pressure in the vacuum container is 1 × during film formation.
It was 10 ⁻⁶ Torr. RHE of this GaN laminated thin film
When the ED pattern was observed, a streak pattern was observed, and it was found that the surface flatness and crystallinity were good. The carrier density of this GaN thin film was measured by the Van der Pauw method to find that it was 7 × 10 ¹⁷ / cm 3.
^{Was 3} . When the photoluminescence was measured at 300 K, a spectrum having a peak near 3.4 eV was obtained.

[0042]

Example 5 Gas source MBE method using nitrogen trifluoride
To an example of growing a GaN thin film on a sapphire substrate
explain about. First, vacuum container 1 and ammonia
Bake the gas line at 180 ℃ for 100 hours
To do. Heat the substrate 8 at 1100 ° C. for 15 minutes.
Set it in the substrate heating holder inside the vacuum container. Furthermore
The evaporation crucible 2 containing Ga at 1150 ° C. for 3 hours
Heating was performed and degassing was performed in advance. In a vacuum container
The carbon-containing impurities were measured by the quadrupole mass spectrometer 9.
About 1 × 10 carbon monoxide ^-11Torr, carbon dioxide
Is 3 × 10^{ー 11}Carbon-containing compounds such as Torr and methane
It could not be detected.

As the substrate 8, a sapphire R surface having a size of 20 mm square and an off angle of 0.8 degrees or less is used. After that, the substrate temperature is 700 ° C. and the evaporation crucible 2 is 1020 ° C.
Heated to. To introduce nitrogen trifluoride, a cracking gas cell 6 filled with alumina fibers inside is used,
The substrate was heated to 200 ° C., and nitrogen trifluoride was directly blown onto the substrate 8 to supply the nitrogen at a rate of 6 cc / min.
The film formation rate was 1.0 Å / sec, and a GaN thin film having a film thickness of 0.8 μm was produced.

The pressure in the vacuum container is 1 × during film formation.
10^-6It was Torr. RHE of this GaN laminated thin film
Observation of the ED pattern shows a streak pattern.
It was found that the surface flatness and crystallinity were good.
It was. In addition, the carrier density of the GaN thin film
・ 5 × 10 when measured by Poe method ¹⁷/ Cm³so
there were. Measure photoluminescence at 300K
The spectrum with a peak near 3.4 eV
was gotten.

[0045]

Example 6 Gas source MBE using ammonia gas
An example of manufacturing a light emitting element using a Ga _1-x In _x N stack grown by the method will be described. The apparatus uses a gas source MBE equipped with evaporation crucibles 2 and 3, an evaporation crucible 5a, a cracking gas cell 6, and a substrate heating holder 7 in a vacuum container 1 as shown in FIG.

First, the vacuum vessel 1 and the gas line for introducing ammonia are baked at 180 ° C. for 100 hours. The substrate 8 is heat-treated at 1100 ° C. for 15 minutes,
Set on the substrate heating holder in the vacuum container. The evaporation crucible 2 containing Ga was 1150 ° C., the evaporation crucible containing In was 800 ° C., and the evaporation crucible containing Zn was 230.
Degassing was performed in advance by heating each at 3 ° C. for 3 hours. When the carbon-containing impurities in the vacuum container were measured by the quadrupole mass spectrometer 9, carbon monoxide was 1 × 10 ^−11.
Torr, carbon dioxide was 2 × 10 ^-11 Torr, and carbon-containing compounds such as methane could not be detected.

As the substrate 8, a surface obtained by rotating the sapphire R surface having a size of 20 mm square by 9.2 degrees with the R surface projection of the sapphire axis as the rotation axis is used. Thereafter, the substrate temperature was heated to 700 ° C., the evaporation crucible 2 was heated to 1020 ° C., the evaporation crucible 3 was heated to 660 ° C., and the evaporation crucible 4 was heated to 190 ° C.
A cracking gas cell 5 having alumina fibers filled therein was used to introduce the ammonia gas, heated to 300 ° C., and supplied at a rate of 7 cc / min so that the gas was directly blown onto the substrate 8. First, the shutter for the Ga and In evaporation crucible was opened, and an n-Ga _1-x In _x N mixed crystal layer (x = 0.05) with a film thickness of 0.6 μm was formed at a film formation rate of 1.5 Å / sec. Create. Then, the shutters for the Ga and In evaporation crucibles and the Zn evaporation crucible were simultaneously opened, and the film thickness was set to 50 Å / sec.
By forming a 0-type p-type doping layer, p-G
a _1-x In _x N mixed crystal layer (x = 0.05) is grown, and Ga
_1-x In x N mixed crystal (x = 0.05) was prepared laminated structure.

This Ga _1-x In _x N mixed crystal (x = 0.0
5) When the RHEED pattern of the laminated thin film was observed, a streak pattern was observed, and it was found that the surface flatness and the crystallinity were good. In addition, this Ga _1-x In _x
When the photoluminescence of the N mixed crystal (x = 0.05) laminated thin film was measured at 300 K, a spectrum having a peak near 2.6 eV was obtained.

Then, by applying a fine processing process, an element pattern as a light emitting element and an electrode are formed. The lithography process can be performed by a process using an ordinary photoresist material, and an element pattern and an electrode are formed by an ion milling method as an etching method. Then,
Al for the n-Ga _1-x In _x N mixed crystal (x = 0.05) layer
On the p-Ga _1-x In _x N mixed crystal layer (x = 0.05), an Au electrode is formed by a vacuum evaporation method.

The element wafer obtained by this method was cut with a dicing saw, wiring was performed using Au wires with a wire bonder, and then packaged with an epoxy resin. The structure of the device of the present invention is shown in FIG. When a voltage of 15 V was applied to this device and a current of 20 mA was injected, light emission of 60 mcd was observed. The emission spectrum had a peak near 480 nm and was blue emission.

[0051]

According to the thin film growth method of the present invention, a gallium nitride semiconductor thin film having excellent surface flatness and crystallinity can be obtained, and a gallium nitride based semiconductor thin film which is particularly suitable as a purple to blue semiconductor light emitting device. Can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a gas source MBE apparatus used for thin film production.

FIG. 2 is a photograph showing an RHEED pattern of a crystal structure of a GaN thin film produced in Example 1 (electron beam is incident parallel to a-axis of GaN).

FIG. 3 is a photograph showing an RHEED pattern of a crystal structure of a GaN thin film produced in Comparative Example 1 (an electron beam is incident parallel to the a-axis of GaN).

FIG. 4 is a result of measuring photoluminescence of the GaN thin film manufactured in Example 1.

5 is a photoluminescence measurement result of the GaN thin film produced in Comparative Example 1. FIG.

FIG. 6 is a view showing a cross-sectional view of a GaNMIS type structural element manufactured in Example 3;

FIG. 7 is a result of current-voltage measurement of the GaNMIS type structural element manufactured in Example 3.

8 is a Ga _{1 -x} In _x N mixed crystal (x
= 0.05) A cross-sectional structure of a light emitting device using a laminated thin film.

[Simple explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Evaporating crucible 3 Evaporating crucible 4 Evaporating crucible 5 E Evaporating crucible 5 B Evaporating crucible 6 Cracking Kugu gas cell 7 Substrate heating holder 8 Substrate 9 Quadrupole mass spectrometer 10 RHEED electron gun 11 RHEED screen 12 Cryopanel 13 Shutter 14 Shutter 15 Shutter 16 E-Shutter 16 Lo-Shutter 17 Valve 18 Cold trap 19 Oil diffusion pump 20 Oil rotary pump 21 Substrate 22 Al electrode 23 n-GaN 24 i-GaN 25 Au electrode 26 n-Ga _1-x In _x N mixed crystal (x = 0.05) 27 p-Ga _1-x In _x N mixed crystal (x = 0.05)

Claims (1)

[Claims] 1. In the production of a gallium nitride-based semiconductor thin film, the thin film growth chamber is kept at a high vacuum, the partial pressure of the carbon-containing compound is maintained at 10 ⁻³ Torr or less, and ammonia gas or nitrogen trifluoride is used as a nitrogen source. A method for growing a gallium nitride-based semiconductor thin film, which comprises supplying the same.