JPH04118921A - Growth method of compound semiconductor crystal - Google Patents

Abstract

PURPOSE:To execute a high-concentration doping operation without worsening a surface morphology and to control a steep impurity concentration by a method wherein a first raw material and a second raw material of elements constituting a compound semiconductor crystal are supplied alternately to the inside of a growth chamber and a doping raw material is supplied to one out of the first raw material and the second raw material or both of them. CONSTITUTION:A substrate 4 is fixed to a carbon susceptor 3 at the inside of a growth chamber constituted of a quartz reaction tube 1. When a compound semiconductor is doped with impurities, raw-material gases are supplied alternately or sequentially by using a changeover valve 7. Then, the raw-material gas which has been supplied previously is adsorbed to the surface of the semiconductor substrate; adsorbed atoms of the raw-material gas are reacted with a reactive gas which has been supplied next; a compound semiconductor is produced and grown. A raw-material gas for a doping operation of impurities is supplied to the growth chamber together with any raw-material gas or all raw-material gases. Thereby, it is possible to solve a problem that a high-concentration doping operation and/or a growth operation at a monomolecular layer unit are impossible.

Description

[Detailed Description of the Invention] [Summary] This method relates to a compound semiconductor crystal growth method that grows crystals in atomic layer units and enables high-concentration doping. With the aim of making it possible to control the impurity concentration, when doping impurities into a binary compound semiconductor crystal, the first raw material of the element constituting the compound semiconductor crystal and the second raw material constituting the compound semiconductor crystal are combined. The doping raw material is alternately supplied into the growth chamber, and the doping raw material is supplied together with either the first raw material, the second raw material, or both. [Industrial Application Field] The present invention relates to a method for growing compound semiconductor crystals, and more particularly to a method for growing compound semiconductor crystals that allows crystal growth in units of atomic layers and enables high concentration doping. Compound semiconductor crystals and their impurity concentrations are being refined to advance the miniaturization of electronic devices and improve their performance, as well as to develop electronic devices with new functions by realizing physical properties not found in conventional bulk materials. There is a strong demand for control on an atomic layer basis. Furthermore, with regard to controlling the concentration of impurities in compound semiconductor crystals, there is a strong demand for the development of techniques for doping with higher concentrations. [Prior art] Conventionally, in organic metal vapor deposition (MOCVD), when growing a high-quality InP crystal, for example, I
Growth was performed by using trimethyl indium (TMI) as the n raw material and phosphine (PH, ) as the p raw material, and simultaneously supplying the raw materials to a reaction tube at a growth temperature of 600°C. [Problems to be Solved by the Invention] When doping an InP crystal at a high concentration using the method described above, the doping concentration tends to be saturated even if the concentration of the doping gas is increased. The curve labeled "Conventional method" in Figure 1 shows the relationship between the impurity concentration and the H2Se flow rate when n-type impurities are doped using hydrogen selenide, Hz Se (Ha dilution 5 ppm) as a doping gas, using the above method. , the impurity concentration is 10
In addition, even if high concentration doping is achieved, the surface morphology of the crystal deteriorates and the thickness of the semiconductor layer becomes non-uniform, resulting in a superlattice structure. Furthermore, when compound semiconductor crystals with heterointerfaces and different impurity concentrations are grown at the aforementioned temperature of 600°C,
Since impurity diffusion occurs during growth, it is difficult to control the impurity concentration steeply with the precision of a monoatomic layer. Therefore, an object of the present invention is to provide a compound semiconductor crystal growth method that enables high concentration doping without deteriorating surface morphology. A further object of the present invention is to provide a compound semiconductor crystal growth method that allows steep control of impurity concentration. [Means for Solving the Problems J] In the case of growing a binary compound semiconductor crystal, the present invention consists of alternately using a first raw material of an element constituting the compound semiconductor crystal and a second raw material constituting the compound semiconductor crystal. In the case of growing a ternary compound semiconductor crystal, the three elements constituting the compound semiconductor crystal are The gist is to supply the doping raw material into the growth chamber sequentially, and to supply the doping raw material together with any one or more raw material gases. In the present invention, when doping a compound semiconductor crystal with impurities, if the raw material gas is supplied to the growth chamber alternately or sequentially instead of all at once, the raw material gas supplied first is adsorbed on the surface of the semiconductor substrate. The adsorbed atoms of this raw material gas react with the next supplied reaction gas on the substrate to generate and grow a compound semiconductor. The raw material gas for doping with impurities is supplied to the growth chamber together with any or all of the raw material gases. When raw material gas is supplied all at once to the reaction chamber as in the conventional method, the gas phase reaction within the reaction chamber becomes dominant in the rate of crystal growth and incorporation of impurities, resulting in high concentration doping and/or growth in monoatomic layer units. It becomes possible. In order to avoid these problems, the present invention supplies the source gas alternately or sequentially as described above. According to embodiments of the present invention, for example, an InP crystal can be replaced with a conventional M
TMI and PH are added to the raw materials using O-CVD equipment.
, to perform growth by supplying the raw materials alternately. By purging with H2 gas between each supply and expelling the raw material gas from the growth chamber, it is possible to eliminate the mixture of raw material gases in the gas phase. . Growth is performed at a growth temperature of 350° C. using H2 as a carrier gas. Hydrogen selenide (H, Se) or the like is used as a raw material for n-type doping. The growth temperature is 350°C. [Function] According to the invention described in claims 1 and 2, the raw material gas supplied to the growth chamber forms a compound layer of 0 to 1 atomic layer. Since the impurity is doped into the O-l atomic layer, high concentration doping is possible, and the surface morphology of the grown layer is also good. Doping of impurities is thought to be due to adsorption to the substrate, similar to the case of semiconductor constituent atoms. Compared to the case where impurities are incorporated into a compound produced by a chemical reaction as in the conventional method, more atoms can be incorporated, which is considered to enable the high concentration doping of the present invention. In the method according to claim 3, the substrate temperature is considerably lower than in the conventional methods, so that the amount of impurity doped is further increased. The reason why it is possible to grow the compound at such a low temperature is because the raw material gases are supplied alternately or sequentially to carry out the 1n-situ reaction on the substrate itself on which the film is to be formed. Although it is of course possible to carry out the reaction at the same temperature as in the conventional method, this method is extremely preferable when diffusion of impurities is a problem. The method according to claim 4 is particularly effective for producing a heterointerface because the doping is carried out at a high concentration at a low temperature, so that there is little diffusion of impurities from the highly doped compound semiconductor layer to the lightly doped compound semiconductor layer. Although the growth of the low concentration layer may be performed by a conventional method, controlled growth of a monoatomic layer can be performed by performing the method of the present invention in which raw material gases are alternately or sequentially supplied as described in claim 4. Hereinafter, the present invention will be explained in more detail with reference to Examples. [Example] In this example, n-type impurity doping by atomic layer epitaxial growth of InP crystal on an InP (100) substrate will be explained below using a vapor phase growth apparatus conventionally used in MO-CVD method. The first
The results illustrated in the figure as "Example of the present invention" were obtained. In this example, a growth system as shown in FIG. 2 was used. The structure of the growth system is as follows. A substrate 4 is fixed to a carbon susceptor 3 heated by an RF coil 2 in a growth chamber composed of a quartz reaction tube 1. One end of the quartz reaction tube 1 is closed with a lid 5, and an exhaust pipe 7 is attached to a part of it. , which is connected to a vacuum exhaust system via a pressure controller 6. A gas switching valve 7 is connected to the other end of the quartz reaction tube 1, and TMI, TEG, PH, etc. are connected to the gas switching valve 7. Gases such as AsHs and Hs are allowed to flow in, and the pressure of TMI and the like is controlled by an exhaust pipe 9 to which a pressure controller 8 is attached. In this example, growth was performed at a pressure during growth of, for example, 20 Torr and a growth temperature of 350°C. The TMI bubbler temperature was set at 27.1° C., and the raw material was supplied by aerating the H2 carrier. Phosphine as P raw material (HX dilution 20%)
, H2Se (Hz dilution 5pp
m) was used. For example, repeat growth for 1704 cycles, where one cycle consists of the following times and flow rates, and grow InP from 2ooo to
5oo. FIG. 1 shows the results of growing to a human thickness and evaluating the impurity concentration by varying the supply amount of Hs S e (supplied for 0.2 seconds when P Hz was supplied). (Left below) In this example, when performing high-concentration n-type doping at a low temperature of 350°C, TMI is used for the In raw material, TEG is used for the Ga raw material,
Arsine (ASH3゜H2 dilution 20%), n
H2Se (H2 dilution 5 ppm) is used as a type dopant. The growth conditions are as follows. (Left below) The bubbler temperature of each organometallic is shown in parentheses. In this example, almost the same results as in Example 1 were obtained. [Effects of the Invention] The present invention greatly contributes to the development of electronic device materials having several atomic layers of highly concentrated compound semiconductors, or electronic device materials having Peter interfaces made of compound semiconductors with widely different physical properties.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between doping gas supply amount and impurity concentration in an example of the present invention, and FIG. 2 is a conceptual diagram of a growth system used to implement the method of the present invention. 1-Quartz reaction tube, 2-RF coil, 3-carbon susceptor, 4-substrate, 7-exhaust pipe 7.8-pressure controller 8 H2SelE supply amount (SCCM) HzSe supply 1 total amount and degree of layering Related No. 8 7A

Claims (1)

[Claims] 1. When doping a binary compound semiconductor crystal with impurities, a first raw material of an element constituting the compound semiconductor crystal and a second raw material constituting the compound semiconductor crystal are alternately supplied into a growth chamber. A compound semiconductor crystal growth method characterized in that a doping raw material is supplied together with either the first raw material or the second raw material, or both. 2. When doping a ternary compound semiconductor crystal with impurities, the three elements constituting the compound semiconductor crystal are sequentially supplied into the growth chamber, and the doping raw material is supplied together with one or more raw material gases. A method for growing compound semiconductor crystals. 3. The compound semiconductor crystal growth method according to claim 1 or 2, wherein the growth temperature is 300 to 600°C. 4. A first step of growing a first compound semiconductor crystal having an impurity concentration of 10^1^9/cm^3 or more by the method described in any one of claims 1 to 3; Before or after, a second step of growing a second compound semiconductor crystal with an impurity concentration of less than 10^1^9/cm^3 by the method according to any one of claims 1 to 3. A method for growing compound semiconductor crystals.