JP2987967B2 - Epitaxial wafer and its growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a molecular beam epitaxial growth method (hereinafter abbreviated as MBE method) on a GaAs substrate.
The present invention relates to an epitaxial wafer on which a thin film of a compound semiconductor such as GaAs or AlGaAs is stacked and a method for growing the same, and in which HE requires particularly high electron mobility.
It is suitable for use in epitaxial wafers used for producing MT (high electron mobility transistor) and the like.

[0002]

2. Description of the Related Art When a compound semiconductor thin film is epitaxially grown on a GaAs substrate by the MBE method, a plane in which the plane orientation of the conventional substrate coincides with the (001) plane within 0.5 ° or less is used. . (See, for example, JP-A-2-28
In this case, it is known that, under specific growth conditions, micro defects caused by dislocation of the substrate appear on the surface of the epitaxial wafer.

In order to reduce the occurrence of the above minute defects,
Conventionally, growth was performed by appropriately selecting conditions such as growth temperature, arsenic pressure, and growth rate. In general applications such as for low-noise HEMTs and semiconductor lasers, an element having sufficient characteristics is manufactured using a wafer grown on a (001) plane substrate under such conditions that the generation of minute defects can be suppressed. It was possible.

[0004] However, when grown under such conditions, a high mobility HEMT which requires particularly high electron mobility is required.
It was difficult to obtain an epitaxial wafer suitable for the production of Since the conditions for growing an epitaxial wafer having a particularly high electron mobility using the (001) plane substrate coincided with the above-mentioned growth conditions in which micro defects corresponding to dislocations are likely to occur. is there. The growth conditions under which minute defects are likely to occur are as shown by the hatched portions in FIG.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide an epitaxial wafer by the MBE method having few surface micro defects and high electron mobility, and a method of growing the same. I do.

[0006]

According to the present invention, an epitaxial wafer is formed on a GaAs substrate whose plane orientation is inclined at 1 to 5 degrees from a (001) plane or a plane which is crystallographically equivalent thereto.
Laminating a thin film of a compound semiconductor by BE method, rotation of the thin film
An epitaxial wafer having a dislocation density lower than the dislocation density of the GaAs substrate . In the method for growing an epitaxial wafer of the present invention, when growing a compound semiconductor thin film by the MBE method, the temperature of the substrate is set to 560 ° C. to 650 ° C.
The pressure of arsenic is 1 × 10 ⁻³ Pa or more, the growth rate of the thin film is 3 μm / hour or less, and the plane orientation is inclined at 1 to 5 degrees from the (001) plane or a crystallographically equivalent plane. G
Using an aAs substrate, the dislocation density of the thin film
This is a growth method characterized by being smaller than the dislocation density .

[0007]

The present inventors have conducted various studies on the effects of the growth conditions and the plane orientation of the substrate, and have found the following. In other words, GaAs and AlGa under the condition that a wafer having a high electron mobility can be grown by the MBE method (this overlaps with the condition within the range shown by oblique lines in FIG. 1).
When As or the like is grown, if a (001) plane GaAs substrate is used, many minute surface defects occur, but (001)
If a substrate inclined from 1 to 5 degrees from the surface is used, a minute surface defect hardly occurs. This is because the use of a substrate tilted from the (001) plane causes an extremely large number of atomic steps to be grown at the crystal growth position on the substrate surface, so that the effect of dislocation on the substrate is almost eliminated. It is believed that there is.

[0008]

[Example] [Example] The plane orientation was <1 from the (001) plane.
A GaAs substrate tilted twice in the 10> direction was used, and a GaAs epitaxial layer was grown on the substrate by MBE. The dislocation density of the GaAs substrate was 6 × 10 ⁴ cm ⁻² . The growth conditions were a substrate temperature of 590 ° C., an arsenic pressure of 6 × 10 ⁻³ Pa, and a growth rate of 1 μm / hour. By growing for 2 hours, a GaAs epitaxial layer having a thickness of 2 μm was obtained. On the surface of the GaAs epitaxial growth layer formed in this way, no micro defects caused by dislocation of the substrate were observed. When the electrical characteristics of the grown epitaxial layer were measured, the residual impurity concentration was 5 × 10
Excellent properties of ¹³ cm ^-3 were obtained.

[Comparative Example] A GaAs substrate whose plane orientation coincides with the (001) plane within 0.2 ° is used.
A GaAs epitaxial layer was grown on this substrate by MBE. As the GaAs substrate, a substrate cut out from an adjacent position of the same ingot as that used in the above embodiment was used. As for the growth conditions, the substrate temperature was 590 ° C., the pressure of arsenic was 6 × 10 ⁻³ Pa, and the growth rate was 1 μm / hour, as in the above-described embodiment. By growing for 2 hours, a GaAs epitaxial layer having a thickness of 2 μm was obtained. On the surface of the obtained GaAs epitaxial growth layer, a large number of minute defects caused by dislocation of the substrate were observed. The density of micro surface defects is
It was almost the same as the dislocation density of the substrate. It was confirmed that the epitaxial growth layer had the same electrical characteristics as those of the example.

The conditions for epitaxial growth are not limited to the above embodiment. The substrate temperature during growth is 560
A similar result can be obtained if the temperature is selected within the range of 650 ° C. If the temperature is lower than 560 ° C. or higher than 650 ° C., the mobility of the epitaxial layer is low. Arsenic pressure is 1 × 1
When the pressure is 0 ^-3 Pa or more, an epitaxial layer having good electric characteristics can be obtained. When the growth rate is 3 μm / hour or less, a good epitaxial layer can be obtained. If the plane orientation of the substrate deviates from the (001) plane by less than 1 degree, a micro defect corresponding to the dislocation of the substrate occurs, and if it exceeds 5 degrees, a mirror-like growth surface cannot be obtained.

[0011]

According to the present invention, an epitaxial wafer having few surface micro defects and high electron mobility can be obtained by the MBE method, and has an excellent effect in applications such as a high electron mobility transistor.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between growth conditions and generation of micro defects when a (001) GaAs substrate is used.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C30B 23/08 C30B 29/40-29/42 C30B 25/18

Claims (2)

(57) [Claims] In an epitaxial wafer in which a compound semiconductor thin film is laminated on a GaAs substrate by a molecular beam epitaxial growth method, the plane orientation of the substrate is at least 1 degree from the (001) plane or a plane crystallographically equivalent thereto. Degrees, the dislocation density of the compound semiconductor thin film is
An epitaxial wafer having a dislocation density lower than that of the substrate. 2. When a compound semiconductor thin film is laminated on a GaAs substrate by molecular beam epitaxy to grow an epitaxial wafer, the temperature of the substrate is set to 560 ° C. to 650 ° C.
° C, the arsenic pressure is 1 × 10 ⁻³ Pa or more, the growth rate of the thin film is 3 μm / hour or less, and the plane orientation is (001).
Grown on a GaAs substrate inclined from 1 ° to 5 ° from the surface or a crystallographically equivalent surface ,
The dislocation density of the semiconductor thin film is lower than the dislocation density of the substrate.
Method of growing the epitaxial wafer, characterized in that the decoction.