JPH06191989A - Production of semiconductor crystal thin film - Google Patents

Abstract

PURPOSE:To provide the single crystal thin film laminate structure having steep heterogeneous interfaces even at low temperatures by controlling the growth temperature of the thin film to <= a specific value and specifying both the feeding of raw material substances and the irradiation of atomic hydrogen, etc., or the feeding of the raw material substances, when an Sb,As-containing compound semiconductor crystal thin film-heterogeneous structure is produced on a substrate. CONSTITUTION:An InAs/GaSb heterogeneous thin film layer structure is produced by the use of e.g. an MBE device equipped with a tungsten heater 3. A GaSb wafer is used as a substrate 6, and after a high vacuum evacuation, the substrate 6 is held at a prescribed temperature lower than 400 deg.C. Raw material substances containing elements constituting the thin film are fed in prescribed feeding amounts, respectively. During the growth of the thin film, a prescribed flow volume of hydrogen gas is heated with a heater 3, and the generated atomic hydrogen 4 is irradiated on a substrate. Or, hydrogen plasma is irradiated on the substrate for the growth of the thin film. Or, the substrate 6 is held at a prescribed temperature below 400 deg.C, and prescribed amounts of the raw material substances containing the thin film-constituting elements are intermittently and alternately fed at preset time intervals for the growth of the thin film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heterostructure in which different kinds of compound semiconductor crystal thin films are laminated, and more particularly to a method for producing a heterostructure having a steep interface.

[0002]

2. Description of the Related Art A compound semiconductor crystal thin film represented by InAs / GaSb and containing antimony as a constituent element,
A superlattice structure (so-called type II) formed by alternately stacking compound semiconductor crystal thin films containing arsenic as a constituent element.
The superlattice) has a feature that electrons and holes exist spatially separated from each other, and is regarded as a promising material system for realizing devices having new functions such as quantum effect application devices. In order for a device manufactured using this superlattice structure to exhibit the desired performance, it is a necessary condition that the interface (heterointerface) between the layers forming the superlattice is steep. In addition, the production of such a laminated structure of a compound semiconductor crystal thin film is usually performed by molecular beam epitaxy (Molecular
Beam Epitaxy: Hereinafter referred to as MBE. ) Method.

[0003]

By the MBE method, a compound semiconductor crystal thin film containing arsenic (hereinafter represented by InAs) is grown on a compound semiconductor crystal thin film containing antimony (hereinafter represented by GaSb). If you do
Arsenic is inevitably irradiated on GaSb. G in this case
Fig. 1 shows the results of observing how As entered into aSb.
Shown in. FIG. 1 shows a case where solid arsenic is heated and sublimated from a Knudsen cell in a vacuum to irradiate a GaSb substrate (irradiation amount is 5 × 10 to ⁶ Torr and is constant for 5 minutes). (XPS: X-ray Photoelect
2 shows the relationship between the As3d photoelectron signal intensity (cps: count / second) measured by ron spectroscopy and the temperature (° C.) of the GaSb substrate during irradiation. The black circles in the figure are the XPS measurement results after arsenic irradiation at a predetermined substrate temperature, and the white circles indicate heat treatment at 520 ° C. for 5 minutes after arsenic irradiation at a predetermined substrate temperature. It is the result when it went. It means that the larger the As3d photoelectron signal intensity, the larger the amount of arsenic that has penetrated into the GaSb substrate. As is clear from FIG. 1, when the substrate temperature during arsenic irradiation was higher than 400 ° C., the As3d photoelectron intensity increased sharply, indicating that As atoms penetrated into the GaSb substrate. That is, the InAs layer is
When growing on aSb, As is higher than 400 ° C.
It means that the steepness of the interface between the InAs layer and GaSb is lowered due to the invasion. Moreover, the decrease in the As3d photoelectron signal intensity was slight even after the heat treatment at 520 ° C., indicating that the invaded arsenic is thermally stable. On the other hand, when irradiated at 400 ° C. or lower, As3
The d photoelectron signal intensity is small both after irradiation and after heat treatment, and the change in intensity before and after heat treatment is small. This indicates that the irradiated arsenic is desorbed without entering the GaSb substrate. In the case of irradiation at room temperature, the intensity after irradiation is higher than that at 400 ° C. and 200 ° C., but after the heat treatment, it is almost the same as the intensity after heat treatment when irradiated at these temperatures. From this, at room temperature, part of the irradiated arsenic is deposited on the GaSb substrate,
It shows that it is easily desorbed by heat treatment. From the above results, it is understood that the thin film growth temperature needs to be 400 ° C. or lower in order to obtain a steep hetero interface in which arsenic does not enter in the fabrication of the InAs / GaSb laminated structure. However, it is 400 in the normal MBE method.
It is generally difficult to grow these crystal thin films at a temperature of not higher than 0 ° C. because the growth temperature is too low. That is, InA
The s thin film and the GaSb thin film become amorphous and a single crystal cannot be obtained. Therefore, there is a problem that a high quality hetero laminated structure cannot be obtained and the characteristics of the manufactured device are not good. An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a method for producing a laminated structure of a compound semiconductor crystal thin film capable of obtaining a steep hetero interface in which arsenic does not enter.

[0004]

In order to achieve the above object of the present invention, a semiconductor crystal thin film is formed by laminating a compound semiconductor crystal thin film containing arsenic as a constituent element and a compound semiconductor crystal thin film containing antimony as a constituent element. In the method for producing a heterostructure, the growth temperature of the thin film is set to 400 ° C. or lower, and at the same time as the supply of the raw material containing the thin film constituent elements, atomic hydrogen or hydrogen plasma is irradiated to grow the thin film, or arsenic is grown. In a method for producing a heterostructure of a semiconductor crystal thin film by laminating a compound semiconductor crystal thin film containing as a constituent element and a compound semiconductor crystal thin film containing antimony as a constituent element, the growth temperature of the thin film is set to 400 ° C. or lower, and A predetermined amount of a raw material containing the constituent elements of the compound semiconductor crystal thin film, intermittently at a set time interval,
Further, they are alternately supplied to grow a thin film.

[0005]

The hetero-multilayer thin film of the present invention is manufactured by a single crystal having a steep hetero interface even at a low temperature of 400 ° C. or lower while preventing the entry of As atoms into the compound semiconductor crystal thin film containing Sb as a constituent element. It utilizes the crystal growth characteristic that a laminated structure of thin films can be produced.

[0006]

Embodiments of the present invention will be described below in more detail with reference to the drawings. Example 1 FIG. 2 shows an example of the configuration of a thin film growth apparatus used for producing a thin film in this example. In FIG. 2, 1 is a hydrogen gas inlet, 2 is a hydrogen gas nozzle, 3 is a tungsten heater, 4 is atomic hydrogen produced, 5 is a solid raw material evaporation cell (Knudsen cell) of In, As, Ga and Sb, Reference numeral 6 is a thin film growth substrate, 7 is a thin film crystal growth chamber, and 8 is a connection port to an exhaust pump. This thin film growth apparatus is a normal MBE apparatus in which a hydrogen gas nozzle 2 and a tungsten heater 3 for heating hydrogen gas are added. InAs / GaS using this thin film growth apparatus
In the fabrication of the b-hetero thin film laminated structure, a GaSb wafer having a (100) orientation is used as the thin film growth substrate 6, and after evacuating to a high vacuum, the substrate 6 is kept at a predetermined temperature and a raw material containing thin film constituent elements is added. , And were supplied at the respective supply amounts shown below. That is, metallic indium ... 3 × 10 to ⁷ Torr
(MmHg), solid arsenic ... 1.5 × 10 ~ ⁵ Torr,
Metallic gallium: 3 × 10 to ⁷ Torr, metallic antimony: 6 × 10 to ⁷ Torr. Further, during the thin film growth, a hydrogen gas at a flow rate of 2 sccm (cm ³ / min) was heated to 1800 ° C. by the tungsten heater 3, and the produced atomic hydrogen 4 was irradiated on the substrate. Under such a thin film forming condition, the InAs layer 14 having a film thickness of 120 nm and the film thickness of 120 nm are formed.
The GaSb layer 15 of 1 was used as one cycle to repeat growth of four cycles of the thin film to produce the compound semiconductor crystal thin film having the laminated structure shown in FIG. 4 and 5 show the fabricated InAs and Ga.
Secondary ion mass spectrometry (SIMS) of In, Ga, As, and Sb atoms in the laminated structure of Sb
roscopy) results. The change in secondary ionic strength with depth from the surface is plotted. FIG. 4 shows the case where the substrate temperature is set to 350 ° C. and FIG. 5 is set to 500 ° C.
Both of them are irradiated with atomic hydrogen 4 during the thin film growth of the InAs layer 14 and the GaSb layer 15. In the case of FIG. 4, a steeply changed profile was obtained according to the structure of all four elements. On the other hand, in the case of FIG. 5, In and Ga are
While showing a steep profile similar to the case of A,
s and Sb have a gentle profile. That is, in the case of 350 ° C. growth, A
While a steep hetero interface was obtained without invasion of s into the GaSb layer, remarkable intrusion occurred at 500 ° C. growth, resulting in mixing of group V atoms of the periodic table at the hetero interface. I understand. That is, it is shown that by supplying atomic hydrogen and setting the substrate temperature to 400 ° C. or lower, a hetero thin film laminated structure having a steep depth profile can be manufactured. Also,
In order to observe the crystallinity of the grown thin film at 350 ° C., In
During the thin film growth of the As layer 14 and the GaSb layer 15, the supply of the raw material and atomic hydrogen is interrupted, the surface of the grown thin film is irradiated with a high-speed electron beam, and the reflection electron beam diffraction (RH) from the pole surface layer is performed.
EED: Reflection High Energy Electron Diffractio
n) The image was observed. As a result, a streak-like diffraction pattern showing a surface reconstruction of (2 × 4) is obtained in the case of growing the InAs layer, and (1 × 3) in the case of growing the GaSb layer.
A streak-like diffraction pattern showing the surface reconstruction of was observed, and it was confirmed that a single crystal thin film was grown in both. On the other hand, the RHEED image obtained when the thin film growth was performed at 350 ° C. without irradiating atomic hydrogen shows the InAs layer and GaS.
Both the b layer showed a halo pattern and became an amorphous film, and a single crystal thin film could not be obtained.

<Embodiment 2> FIG. 6 shows an example of the structure of a thin film growth apparatus used for producing a thin film in this embodiment. In FIG. 6, 1 is a hydrogen gas introduction port, 9 is a rectangular microwave waveguide, 10 is a quartz microwave introduction window,
11 is a cavity resonator type plasma generation chamber, 12 is an electromagnet, 1
Reference numeral 3 is plasma, 6 is a thin film growth substrate, 5 is a solid material evaporation cell (Knudsen cell), 7 is a thin film crystal growth chamber, and 8 is a connection port to an exhaust pump. This thin film growth apparatus has a basic structure in which a cavity resonator type plasma generation chamber 11 is connected to an ordinary MBE growth chamber. Plasma was irradiated by transporting the hydrogen plasma 13 generated in the plasma generation chamber 11 provided adjacent to the MBE growth chamber to the thin film growth substrate 6. That is, hydrogen gas and microwave power are introduced into the plasma generation chamber 11, and a magnetic field is applied from an electromagnet 12 installed outside the generation chamber to apply electron cyclotron resonance (ECR: Elec).
Hydrogen plasma 13 is generated by satisfying the tron Cyclotron Resonance condition. The generated hydrogen plasma 13 is transported to the substrate by a divergent magnetic field formed by the electromagnet 12 (a magnetic field intensity distribution in which the intensity decreases from the plasma generation chamber toward the substrate). The generation condition of the hydrogen plasma 13 in the present embodiment is that the hydrogen gas flow rate is 10 sccc.
m, microwave frequency 2.45 GHz, microwave power 100 W, magnetic field strength 875 Ga in plasma generation chamber
It is uss (Gauss). In using this thin film growth apparatus
In the fabrication of the As / GaSb hetero thin film laminated structure, a GaSb wafer having a (100) orientation is used as the thin film growth substrate 6, and after evacuation to a high vacuum, the substrate is kept at a predetermined temperature and is a raw material containing thin film constituent elements. In, As, Ga, S
The substrate was irradiated with b in the supply amounts shown in Example 1, and further, the hydrogen plasma 13 generated under the above conditions during the thin film growth was irradiated on the substrate. The produced laminated structure is
120 nm thick InAs layer and 120 nm thick GaS
The structure was the same as that shown in FIG. 3 of Example 1 in which four cycles were repeated with the b layer as one cycle. The In, Ga, As, and Sb of the laminated structure grown by MBE under this hydrogen plasma irradiation
The results of secondary ion mass spectrometry (SIMS) of each atom were the same as those in FIG. 4 and FIG. 5 of Example 1. That is, when the substrate was grown at a temperature of 350 ° C., As was grown during InAs growth.
While a steep hetero-interface was obtained without invasion of GaSb into GaSb, remarkable intrusion occurred at 500 ° C. growth, resulting in mixing of V group atoms at the hetero-interface. That is, by irradiating with hydrogen plasma and setting the substrate temperature at 400 ° C. or lower, a thin film laminated structure having a steep hetero interface could be manufactured. Also,
Similar to the case of Example 1, RHEED observation of the InAs layer and the GaSb layer was performed for the case of hydrogen plasma irradiation and the case of non-irradiation in the case of 350 ° C. growth. Was grown, but it was found that the thin film without irradiation was amorphous. In this embodiment, an InAs layer and GaS are used.
As the raw material of the layer b, the raw material of the solid element was used as in the usual MBE method, but TMI (trimethylindium),
Organic metal raw materials such as TEAs (triethylarsenic), TMG (trimethylgallium), and TESb (triethylstibine) are used to irradiate hydrogen plasma during thin film growth.
It is possible to grow thin films at low temperatures below 00 ° C. Also,
If hydrogen-diluted AsH ₃ (arsine) or the like is used as a raw material, plasma can be generated only with the raw material gas without supplying the hydrogen gas separately from the raw material, which also enables low temperature growth. Such a thin film growth method is not contrary to the gist of the present invention.

<Embodiment 3> In this embodiment, MBE
An example of manufacturing a hetero thin film laminated structure at low temperature using the apparatus will be described. As mentioned above, normal MB
The InAs layer and the GaSb layer obtained by the E method simply by setting the growth temperature to 400 ° C. or less are not single crystals but amorphous, so that a good laminated structure cannot be realized.
Therefore, as a result of studying a method of supplying a raw material containing a thin film constituent element during MBE growth, a laminated structure composed of thin films excellent in crystallinity even at 400 ° C. or lower by promoting a migration action of the raw material on the substrate. It was found that After the GaSb substrate with the (100) orientation was set to a predetermined temperature with a normal MBE apparatus, the supply of the raw material containing the thin film constituent elements was controlled in time as shown in FIG. 7 to obtain InAs / GaSb. A laminated structure was produced. The supply amounts of In, As, Ga and Sb are the same as those in the first embodiment. The supply and interruption of the raw material were controlled as follows by the shutter provided at the outlet of each cell. That is, the In supply 1 during the growth of the InAs layer 1
Seconds, interruption 2 seconds, As supply 1 second, interruption 2 seconds [Fig. 7 (a), (b)]. In addition, during the growth of the GaSb layer, the Ga supply is 1 second, the interruption is 2 seconds, the Sb supply is 1 second, and the interruption is 2 seconds [FIGS. 7C and 7D]. Furthermore, interruption 2 when switching from the InAs layer to the GaSb layer 2
Second, the switching from the GaSb layer to the InAs layer was interrupted for 1 second. This growth sequence was repeated until a thin film having a desired thickness was obtained. Note that, in FIG. 7, in order to simply display the raw material supply sequence, the height of the vertical axis is expressed the same regardless of the actual raw material supply amount. The manufactured laminated structure has an InAs layer with a thickness of 120 nm and a thickness of 1
The structure is the same as that of FIG. 3 shown in Example 1 in which four cycles of a 20 nm GaSb layer are repeated. In, A of the laminated structure produced by controlling the time of this raw material supply
Secondary ion mass spectrometry (SIM) of each atom of s, Ga, and Sb
The result of (S) was almost the same as that of FIG. 4 and FIG. 5 shown in Example 1. That is, when grown at a substrate temperature of 350 ° C., As does not enter into the GaSb layer during growth of the InAs layer and a steep hetero interface is obtained, whereas at 500 ° C. growth, remarkable penetration occurs. Occurred, and a mixture of group V atoms occurred at the hetero interface. As described above, by alternately supplying the raw materials temporally and setting the substrate temperature to 400 ° C. or lower, a laminated structure having a steep hetero interface could be manufactured. In addition, as in Example 1, 3
RHE of InAs layer and GaSb layer in the case of alternate supply in the case of 50 ° C. growth and in the case of no alternate supply
As a result of ED observation, it was found that a single crystal was grown when alternately supplied, but the thin film was amorphous when not alternately supplied. In the above-mentioned Examples 1, 2 and 3, the case of the laminated structure in which InAs / GaSb is repeated has been described, but it is simply GaS.
It is clear that the method of the present invention is effective even when the InAs layer is simply grown on the b substrate. Moreover, not only InAs / GaSb but also GaAs / GaS
b, AlAs / GaSb, InAs / InSb, GaA
s / InSb, AlAs / InSb, etc.
It is needless to say that the hetero interface having a sharp composition change can be obtained by applying the method of the present invention even to a laminated structure of nGaAsSb / AlGaAsSb of quaternary mixed crystals.

[0009]

As described above in detail, the A of the present invention
According to the method for producing a hetero structure in which a compound semiconductor crystal thin film containing s as a constituent element and a compound semiconductor crystal thin film containing antimony as a constituent element are stacked, a hetero structure having a steep interface in which As does not enter is prepared. Thus, a high-performance compound semiconductor crystal thin film can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing the dependence of As3d intensity from a GaSb substrate irradiated with As on the substrate temperature during irradiation.

FIG. 2 is a schematic diagram showing an example of the configuration of a thin film growth apparatus used in Example 1 of the present invention.

FIG. 3 shows InAs / GaS produced in Example 1 of the present invention.
b A schematic diagram showing the configuration of a laminated structure.

FIG. 4 is a diagram showing the distribution of the concentration of each element in the depth direction in the InAs / GaSb laminated structure produced (grown at 350 ° C.) in Example 1 of the present invention.

FIG. 5 is a diagram showing the distribution of the concentration of each element in the depth direction in the InAs / GaSb laminated structure produced (grown at 500 ° C.) in Example 1 of the present invention.

FIG. 6 is a schematic diagram showing an example of the configuration of a thin film growth apparatus used in Example 2 of the present invention.

FIG. 7 is an explanatory diagram showing a raw material supply sequence used in Example 3 of the present invention.

[Explanation of symbols]

 1 ... Hydrogen gas inlet 2 ... Hydrogen gas nozzle 3 ... Tungsten heater 4 ... Atomic hydrogen 5 ... Solid source evaporation cell (Knudsen cell) 6 ... Thin film growth substrate 7 ... Thin film crystal growth chamber 8 ... Exhaust pump connection Mouth 9 ... Rectangular microwave waveguide 10 ... Quartz microwave introduction window 11 ... Cavity resonator type plasma generation chamber 12 ... Electromagnet 13 ... Hydrogen plasma 14 ... InAs layer 15 ... GaSb layer 16 ... GaSb substrate

Claims (2)

[Claims] 1. A semiconductor crystal in which a predetermined substrate is disposed in a thin film growth chamber, and a compound semiconductor crystal thin film containing antimony as a constituent element and a compound semiconductor crystal thin film containing arsenic as a constituent element are stacked on the substrate. In the method for producing a heterostructure of a thin film, the growth temperature of the compound semiconductor crystal thin film is maintained at 400 ° C. or lower, and atomic hydrogen or hydrogen plasma is irradiated onto the substrate at the same time as the supply of a raw material containing thin film constituent elements. A method for producing a semiconductor crystal thin film, comprising at least a step of growing a thin film by means of a method. 2. A semiconductor crystal in which a predetermined substrate is provided in a thin film growth chamber, and a compound semiconductor crystal thin film containing antimony as a constituent element and a compound semiconductor crystal thin film containing arsenic as a constituent element are laminated on the substrate. In a method for producing a heterostructure of a thin film, the growth temperature of the compound semiconductor crystal thin film is maintained at 400 ° C. or lower, a raw material containing each of the thin film constituent elements, a predetermined amount, intermittently at a set time interval,
A method for producing a semiconductor crystal thin film, which further comprises at least a step of alternately supplying onto the substrate to grow a thin film.