JPH0633228B2 - Molecular beam epitaxy growth method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a molecular beam epitaxial growth method, and particularly to a III-V group compound semiconductor using a group V element compound containing phosphorus (P) and a group III element. The present invention relates to a molecular beam epitaxial growth method for growing a crystal.

[Conventional technology]

The molecular beam epitaxy method is a method of growing single crystal thin films on a substrate by placing each constituent element of the crystal in a separate crucible and heating and evaporating them in an ultrahigh vacuum. This molecular beam epitaxial method is currently expected as a crystal growth method with the best control of thin films.

However, in the conventional type molecular beam epitaxial growth method, since a solid raw material is mainly used, the raw material is depleted and the growth chamber is exposed to the atmosphere to supplement the raw material. This not only takes a long time to return the growth chamber to the ultra-high vacuum, but also poses a problem in terms of the quality of the epitaxial film.

The conventional molecular beam epitaxial growth method is, for example, Ga
The growth of a crystal containing only one type of V group element such as AlAs mixed crystal was good, but the growth of a crystal containing two or more types of V group element such as InGaAsP mixed crystal was difficult. The cause of this is that in order to obtain a mixed crystal having a desired composition ratio, it is necessary to accurately control the ratio of the molecular beam intensities of two or more kinds of group V molecules. However, when a group V solid raw material is used, the vapor pressure of the raw material is high and it is difficult to control the molecular beam intensity ratio.

Therefore, as a growth method for compensating for such drawbacks, a molecular beam epitaxial growth method using a gas raw material is performed instead of the conventional solid raw material. For example, AR Calawa's 1981 Applied Physics letter.
s) Volume 38, p. 701, As system, P
AsH ₃ and PH ₃ are used for the system compounds.

Fig. 2 shows a cross-sectional view of a general AsH ₃ and PH ₃ introduction part. As
H _3, PH ₃ As ₁ at the pyrolysis furnace for heating using a tantalum filament 12 in tantalum outer pipe 11 is introduced through a leak valve 6 at the introduction portion of the ultra-high vacuum system (gas cell) for, The molecular beam of As ₂ , As ₄ , P ₂ , etc. is formed and grown.

In addition, MB Panish and S.
S.Sumski decomposes AsH ₃ and PH ₃ in a pyrolysis furnace as shown in Fig. ₃ to grow InGaAsP-based mixed crystals.
Prototyped nGaAsP / InPDH laser, which was published in 1984, Journal of Applied Physics.
Applied Physics) 55, p. 3571. As shown in FIG. 3, this pyrolysis furnace has a hole for leaking at the tip of the gas introduction pipe 5 in the resistance heating furnace 13 made of alumina, and the supply amount is changed by changing the pressure of AsH ₃ or PH _3. Are in control.

As described above, the molecular beam epitaxial growth method using a gas as the group V raw material can control the group V molecular beam intensity as compared with the conventional solid source molecular beam epitaxial method.
It is known that a mixed crystal system containing two or more kinds of Group V elements can be grown.

[Problems to be solved by the invention]

However, the conventional molecular beam epitaxial method using a group V gas raw material has a drawback that it is difficult to rapidly change the gas composition. In the conventional molecular beam epitaxial method using a group V gas source, the composition of the group V element is changed by changing the leak valve or the gas pressure, but the molecular beam intensity in the ultra-high vacuum system does not change rapidly. It was This is due to the phenomenon that P ₂ , P ₄ are attached, adsorbed, and re-evaporated particularly near the exit of the pyrolysis furnace, and even if the PH ₃ flow rate is suddenly cut off, molecular beams such as P ₂ will remain for a while. It is thought that it is because it has occurred. Even if a shutter was used, this phenomenon was not completely prevented because it was adsorbed in the form of P ₄ on the shutter and re-evaporated.

INDUSTRIAL APPLICABILITY The present invention takes advantage of the feature that the molecular beam intensity of the V group, which is the feature of the molecular beam epitaxial growth method using a V group gas raw material, can be accurately controlled, and the sharp V group molecular beam that is the drawback of the method It is an object of the present invention to provide a molecular beam epitaxial growth method capable of changing the strength.

[Means for solving problems]

The molecular beam epitaxial growth method of the present invention uses a group V element compound containing phosphorus (P) and a group III element for III-V.
In the molecular beam epitaxial growth method for growing a group compound semiconductor crystal, diphosphine (P ₂
H ₄ ) is used, and a photodecomposition is performed using an excitation light source having a wavelength of 100 nm or more and 260 nm or less.

[Action]

It is known that diphosphine is an unstable substance as compared with phosphine and decomposes when irradiated with ultraviolet rays at room temperature. According to Kawasaki, the absorption wavelength of the photolysis reaction of P ₂ H ₄ is 2
It is known that the maximum absorption wavelength is 60 nm or less and the maximum absorption wavelength is 220 nm or less (Masahiro Kawasaki: Applied Physics, 53, 19).
85, 603). As a power source for the photoexcitation process,
For example, Nikkei Microdevice, Spring 1985, 61-
As shown on page 78, it is the actual situation that it is currently difficult to obtain light having a wavelength of 100 nm or less. Therefore, by irradiating light of the above wavelength with diphosphine as the P feed gas, the P molecular beam can be stably obtained without using the thermal decomposition furnace. Moreover, since the light irradiation is performed in the space of the ultra-high vacuum system, the adsorption phenomenon of P ₂ and P ₄ unlike in the case of the pyrolysis furnace does not occur. Therefore, it is possible to change the P molecular beam intensity rapidly.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a molecular beam epitaxial growth apparatus for explaining an embodiment of the present invention. A case of forming an InP / InGaAs superlattice structure on an InP substrate will be described below with reference to FIG. In FIG. 1, the InP substrate 2 was installed in the vacuum chamber 1 evacuated to an ultrahigh vacuum of about 10 ⁻⁹ Torr, and the substrate temperature was set to 300 ° C. by the heater 3. The group III raw material is obtained by heating high-purity InGa in the ordinary cell 4 to obtain a molecular beam. As As the group V element, AsH ₃ was introduced into the ultrahigh vacuum system from the introduction pipe 5a through the leak valve 6a to obtain arsenic molecular beam in the ordinary pyrolysis furnace 7. Regarding P, P ₂ H ₄ was introduced into the ultrahigh vacuum system from the introduction tube 5b through the leak valve 6b, and the mercury lamp 8 was used to irradiate the P ₂ H ₄ raw material beam with ultraviolet rays through the light irradiation window 9.

During the growth of the InP layer, the Ga molecular beam was blocked by the shutter 10, the AsH ₃ raw material was closed by a leak valve, and further blocked by the shutter. When growing the InGaAs layer, the P ₂ H ₄ raw material was closed by closing the leak valve and interrupting the light irradiation. The AsH ₃ pyrolysis furnace was set at 700 ° C.

In this way, an InGaAs / InP superlattice structure of 50 A period
Layers were grown. As a result, a good mirror growth layer was obtained.

Furthermore, as a result of measuring the concentration of As and P atoms in the depth direction with a secondary ion mass spectrometer (SIMS), the interface is very good, and the P atom concentration, which is a feature of the present invention, changes sharply at the interface. Was confirmed.

〔The invention's effect〕

Using a Group V element compound containing P and a Group III element III
In performing the molecular beam epitaxial growth of a group V compound semiconductor crystal, P ₂ H ₄ (diphosphine) was used as a P supply source gas and photodecomposed in a space in an ultrahigh vacuum system using an excitation light source having a wavelength of 100 nm or more and 260 nm or less. Since the material is used, a pyrolysis furnace is not required when the molecular beam intensity of the group V element is rapidly changed. Therefore, there is no phenomenon in which the P atom concentration change at the growth interface due to the adsorption and re-evaporation of phosphorus does not become steep and spreads, and a grown crystal having a good interface can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a molecular beam epitaxial growth apparatus for explaining an embodiment of the present invention, FIG. 2 is a cross-sectional view of a conventional molecular beam epitaxial growth apparatus where AsH ₃ and PH ₃ are introduced, and FIG. It is sectional drawing of the thermal decomposition furnace which used Panish. 1 ... Vacuum chamber, 2 ... InP substrate, 3 ... Heater, 4 ... Group III raw material cell, 5a, 5b ... Gas introduction pipe, 6a, 6b ... Leak valve, 7 ... Ordinary pyrolysis furnace , 8 ... Mercury lamp, 9 ... Light irradiation window, 10 ... Shutter, 11 ... Tantalum outer tube, 12 ... Tantalum filament, 13 ... Alumina resistance heating furnace.

Claims (1)

[Claims] 1. A molecular beam epitaxial growth method for growing a III-V group compound semiconductor crystal using a group V element compound containing phosphorus and a group III element, wherein diphosphine is used as a phosphorus source gas and the wavelength is 100 nm or more and 260 nm.
A molecular beam epitaxial growth method characterized by photolysis using the following excitation light source.