JP2001102568A - Iii-v compound semiconductor epitaxial wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a III-IV compound semiconductor epitaxial wafer with improved electrical characteristics. SOLUTION: Since an In composition near the hetero-interface of a channel layer 30 constituted of InGaAs is similar to that of an electron supply layer 4, constituted of InGaP and In composition in the channel layer 30 changes continuously, the diffusion of In atoms is suppressed, and superior interface steepness is obtained. Thus, HEMT of high electron mobility is obtained by using such a III-V compound semiconductor epitaxial wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a group III-V compound semiconductor epitaxial wafer.

[0002]

2. Description of the Related Art Generally, in order to epitaxially grow a thin film crystal of a group III-V compound semiconductor on a crystal substrate surface,
Multiple III substrates are placed on the heated crystal substrate in the reactor.
This is performed by feeding a carrier gas containing a source gas of a group V element or a group V element, and thermally decomposing these source gases on a crystal substrate.

FIG. 4 is a cross-sectional view of a conventional III-V compound semiconductor epitaxial wafer.

The epitaxial wafer shown in FIG.
On an As substrate 1, a 200 nm thick un-GaAs layer 2 and a 15 nm thick un-In _0.15 Ga _0.85 As layer 3
And a two-dimensional electron gas concentration of 2e18 cm ^-3 at a thickness of 25 nm.
And n-Ga _0.52 In _0.48 P layer 4 are sequentially grown and laminated.

A high electron mobility transistor called HEMT is one of devices using a heterojunction produced by laminating different kinds of crystals by such a crystal growth method. The HEMT is basically composed of a high-purity layer (for example, InGaAs of an As-based compound semiconductor crystal) and a doping layer (for example, P-based) having a function of supplying electrons by being doped with a smaller electron affinity than the high-purity layer. An electrode is provided on a layered structure having a selective doping structure consisting of two layers of a compound semiconductor crystal (InGaP) and a field effect transistor.

[0006]

By the way, electrons are accumulated two-dimensionally on the high-purity layer side of the interface between these layers. Since the electrons are formed in the high-purity layer, the electron mobility is very high. The electron gas is controlled by an electric field effect by a bias voltage applied to the gate electrode. At this time, if the composition is not switched sharply at the heterojunction interface, the electrons are scattered by the unevenness of the interface and the electrically active crystal defects,
Electron mobility decreases.

In the above-described compound semiconductor using In, In is easily diffused at the interface, and it is difficult to form a steep hetero interface.

In order to prevent the diffusion of In and improve the steepness of the interface, it is desirable that the growth temperature be low. However, disadvantages of this low temperature include the problem that impurities are mixed into the crystal (C, O, etc.) and the doping efficiency is reduced.

Accordingly, an object of the present invention is to provide a group III-V compound semiconductor epitaxial wafer which solves the above problems and has improved electrical characteristics.

[0010]

In order to achieve the above object, a group III-V compound semiconductor epitaxial wafer according to the present invention comprises, on a substrate, a channel layer and an electron supply layer having an electron affinity smaller than that of the channel layer. In the formed III-V compound semiconductor epitaxial wafer, the substrate is GaAs.
, The channel layer is made of InGaAs, the electron supply layer is made of InGaP, the thickness of some layers near the interface of the channel layer is less than or equal to the critical thickness, and has the same In composition as InGaP. .

In addition to the above structure, the III-V compound semiconductor epitaxial wafer of the present invention has an electron supply layer having an In composition of 0.484 lattice-matched to the GaAs substrate, and a partial layer near the channel layer interface. It is preferable that the film thickness be equal to or less than the critical film thickness and the In composition be 0.484.

In addition to the above structure, the III-V compound semiconductor epitaxial wafer of the present invention is characterized in that the In composition of a part of the layer near the interface of the channel layer continuously changes from 0.484 from the interface to the termination to the design composition. Preferably.

In addition to the above constitution, in the group III-V compound semiconductor epitaxial wafer of the present invention, the thickness of a part of the channel layer in which the In composition changes continuously is preferably 1 to 10 nm.

Generally, the degree of diffusion of atoms in a crystal is determined by temperature and concentration gradient. In a conventional epitaxial wafer having a heterojunction structure, discontinuity of the In concentration occurs at the hetero interface, so that In diffusion at the interface occurs more remarkably.

Therefore, the present inventors set the In composition near the heterointerface of the channel layer made of InGaAs to be In composition.
By making the composition the same as that of the electron supply layer made of GaP and continuously changing the In composition in the channel layer,
It has been found that diffusion of In atoms is suppressed and excellent interface steepness can be obtained. Therefore, when an HEMT is manufactured using such an epitaxial wafer having excellent electric characteristics, a HEMT having high electron mobility can be obtained, and high-speed signal processing can be performed.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of a group III-V compound semiconductor epitaxial wafer of the present invention.

The epitaxial wafer shown in FIG. 1 is a group III-V compound semiconductor epitaxial wafer having a substrate 1 on which a channel layer 3 and an electron supply layer 4 having an electron affinity smaller than that of the channel layer 3 are formed. Substrate 1 is GaAs
s, the channel layer 3 is made of InGaAs, the electron supply layer 4 is made of InGaP, the thickness of some layers near the interface of the channel layer 3 is less than the critical thickness, and
It has the same In composition as GaP.

This epitaxial wafer is made of InGaAs.
Since the In composition near the hetero interface of the channel layer 3 made of In has the same composition as the composition of the electron supply layer 4 made of InGaP, and the In composition in the channel layer 3 changes continuously, Diffusion is suppressed, and excellent interface steepness is obtained. By using such an epitaxial wafer having excellent electrical characteristics, a high electron mobility HEM can be obtained.
T can be made.

[0020]

EXAMPLE An epitaxial wafer having a structure with an In composition modulation layer in which the In composition was continuously changed from 0.48 to 0.15 as shown in FIG. 1 was produced. That is, FIG.
The epitaxial wafer shown in FIG. 1 has an un-GaAs layer 2 having a thickness of about 200 nm, an un-In _0.15 Ga _0.85 As layer 3 a having a thickness of about 13 nm, and an un-In _0.48 layer having a thickness of about 1 nm on a GaAs substrate 1. _{→ 0.15} Ga _{0.52 → 0.85}
As layer 3b and un-In _0.48 Ga _0.52 about 1 nm thick
An As layer 3c and an n-Ga _0.52 In _0.48 P layer 4 having a thickness of about 25 nm and a two-dimensional electron gas concentration of about 2e18 cm ⁻³ are sequentially laminated.

FIG. 2 is a view showing a gas sequence during the growth of the epitaxial wafer shown in FIG.

A GaAs substrate 1 having a diameter of 4 inches is placed on a susceptor (not shown), and the temperature of the susceptor is heated to 600 ° C., which is the growth temperature of a thin film. Susceptor is about 11r
Rotated at pm. In this state, the InGaAs layer 30 (3a, 3b, 3c) is supplied from a gas inlet (not shown) of the growth chamber.
Hydrogen diluted trimethylgallium (T
MG), trimethylindium (TMI) and arsine (AsH ₃ ) with varying flow rates, about 15.0.
After the sec growth is stopped, a mixed gas of trimethyl indium (TMI), triethyl gallium (TEG), phosphine (PH ₃ ) and disilane (H ₆ Si ₂ = SiH ₃ SiH ₃ ), which are source gases of the GaInP layer 4, is supplied. By doing so, an epitaxial wafer is obtained.

As a result, the electron mobility of the conventional epitaxial wafer shown in FIG. 4 is 3500 cm ² V ⁻¹ sec.
^In contrast, the electron mobility of the epitaxial wafer of the present invention shown in FIG. 1 was 4800 cm ² V ⁻¹ sec.
High electron mobility of ^-1 was obtained. FIG. 3 is a diagram showing a carrier concentration profile obtained by the CV measurement. The horizontal axis is the depth axis, and the vertical axis is the two-dimensional electron gas concentration axis. In the same figure, the broken line shows the carrier concentration profile of the epitaxial wafer of the present invention, and the solid line shows the carrier concentration profile of the conventional epitaxial wafer.

As shown in the figure, those having a high electron mobility are un-
It can be seen that electrons are confined at the interface between the GaAs layer and the channel layer, and the peak of the two-dimensional electron gas increases. Therefore, it has been found that by continuously changing the In composition in the channel layer, the interface steepness can be realized, and the effect of increasing the electron mobility can be obtained. Therefore, by manufacturing a HEMT using the epitaxial wafer shown in FIG. 1, a HEMT having a high electron mobility can be obtained, and excellent electrical characteristics that can respond to a high-speed signal can be obtained.

Here, InGaP and In at the hetero interface are used.
The optimum condition is that the In composition with GaAs is equal.
However, the thickness of the composition modulation portion near the interface of the InGaAs layer must be equal to or less than the critical film thickness. However, if the thickness is too small, a discontinuous portion of the composition occurs, and the characteristics are degraded. This structure depends on the structure and growth conditions of the p-HEMT epitaxial wafer, and must be suppressed by trial and error.

In this embodiment, an example of the growth of a thin film for an electronic device has been described. However, the III-V compound semiconductor epitaxial of the present invention can be applied to the growth of a thin film for a laser as long as the device uses a heterojunction.

[0027]

In summary, according to the present invention, the following excellent effects are exhibited.

It is possible to provide a III-V compound semiconductor epitaxial wafer having improved electrical characteristics.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a group III-V compound semiconductor epitaxial wafer of the present invention.

FIG. 2 is a view showing a gas sequence when the epitaxial wafer shown in FIG. 1 is grown.

FIG. 3 is a diagram showing a carrier concentration profile obtained by CV measurement.

FIG. 4 is a cross-sectional view of a conventional III-V compound semiconductor epitaxial wafer.

[Explanation of symbols]

1 GaAs substrate 2 Channel layer (un-GaAs layer) 3a Channel layer (un-In _0.15 Ga _0.85 As layer) 3b Channel layer (un-In _{0.48 → 0.15} Ga
_{0.52 → 0.85} As layer) 3c channel layer (un-In _0.48 Ga _0.52 As layer) 4 electron supply layer (n-Ga _0.52 In _0.48 P layer, GaIn
P layer) 30 Channel layer (InGaAs layer)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01S 5/323 // H01L 29/20 F term (Reference) 4G077 AA03 BE47 DB01 ED06 EF03 5F045 AB10 AB17 AC01 AC08 AC19 AD10 AF04 BB05 BB12 BB16 CA07 CA12 DA52 DA58 DA66 5F073 CA07 CB02 DA05 5F102 FA00 GB01 GC01 GD01 GJ05 GK05 GL00 GL04 GL07 GL08 GL16 GL17 GM04 GM10 GQ01 HC01

Claims (4)

[Claims] 1. A semiconductor device comprising: a substrate, a channel layer, and an electron supply layer having an electron affinity smaller than that of the channel layer.
In the IV compound semiconductor epitaxial wafer, the substrate is made of GaAs, and the channel layer is made of InGa.
As, the electron supply layer is made of InGaP,
A III-V compound semiconductor epitaxial wafer, wherein the thickness of a part of the layer near the interface of the channel layer is equal to or less than the critical thickness and has the same In composition as InGaP. 2. The electron supply layer has an In composition of 0.484 lattice-matched to a GaAs substrate, a thickness of a part of the layer near an interface of the channel layer is less than a critical thickness, and an In composition. The III-V compound semiconductor epitaxial wafer according to claim 1, wherein is 0.484. 3. The group III-V compound according to claim 2, wherein the In composition of a part of the layer near the interface of the channel layer continuously changes from 0.484 to the design composition from the interface to the terminal. Semiconductor epitaxial wafer. 4. The III-V compound semiconductor epitaxial wafer according to claim 3, wherein the thickness of a part of the channel layer in which the In composition continuously changes is 1 to 10 nm.