JPH07211642A - Vapor phase epitaxial growth method for compound semiconductor - Google Patents

Abstract

PURPOSE:To allow growth of a high quality crystal without impeding the capturing of carbon impurities. CONSTITUTION:Crystal quality can be enhanced while sustaining the capturing efficiency of dopant by employing an OFF substrate having crytal face orientation inclining from (100) face or equivalent face toward [Oil] or equivalent direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase growth method for a compound semiconductor having a compound semiconductor laminated structure.

[0002]

2. Description of the Related Art Conventionally, a substrate having a low index face such as a (100) face has been used for vapor phase growth of a compound semiconductor aiming at device application. The reason is that the high-index plane has low symmetry, so asymmetry appears in various physical property constants and etching shapes, and there are restrictions such as the fact that the azimuths must be aligned when manufacturing the element and the cleavage plane cannot be used. This is because it occurs. Further, an exponential surface, which is difficult to grow depending on the growth conditions such as the (111) B surface, is not suitable for such purpose. On the other hand, in the low-index plane, the atomic layer step or kink surface density of the crystal surface, which is a site where the group III and V atoms that are the constituent materials of the crystal are efficiently incorporated into the crystal, is low, so the surface morphology and crystal There was a problem that quality etc. deteriorated.

To solve such a problem,
A method of using a substrate in which the plane orientation of the substrate is slightly inclined from the (100) plane or a plane equivalent to this (100) plane to the [011] direction or a direction equivalent to this [011] direction has been proposed. The effect of improving the condition and crystal quality is obtained. This effect is to increase the density of steps by inclining the substrate to increase the efficiency of uptake of atoms, or to incline the substrate in the [011] direction or its equivalent direction to arrange only Ga atoms in steps. This can be achieved by weakening the affinity between the impurity element to be incorporated in the crystal and the atoms present in the step and increasing the crystal purity.

[0004]

However, according to such a method, the incorporation of residual impurities into the crystal is reduced, and at the same time, the incorporation of additional impurities (dopants) essential for growing the device structure is obstructed. Therefore, there is a problem that a desired impurity concentration cannot be obtained.

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems, and its object is to provide a high-quality compound in a vapor-phase growth method of a compound semiconductor without inhibiting the incorporation of carbon impurities. It is an object of the present invention to provide a vapor phase growth method for a compound semiconductor that enables crystal growth.

[0006]

In order to achieve such an object, the method for vapor phase growth of a compound semiconductor according to the present invention comprises:
Crystal growth is performed using an off-substrate in which the plane orientation of the substrate is inclined from the (100) plane or a plane equivalent to this (100) plane to the [0 bar 11] direction or the direction equivalent to this [0 bar 11] direction. It is the one. In another vapor phase growth method of a compound semiconductor according to the present invention, the off-substrate tilt angle is set in the range of 1 to 10 degrees, and the growth temperature of the carbon-added layer is set to 580 ° C. or higher for crystal growth. It was done like this.

[0007]

In the present invention, the crystal quality can be improved while keeping the efficiency of incorporating the added impurities equal.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. As an embodiment of the present invention, a case of crystal growth of an AlGaAs / GaAs heterojunction bipolar transistor (HBT) by a metal organic chemical vapor deposition (MOCVD) method will be described as an example. FIG. 1 shows an embodiment in which the present invention is applied to the growth of a carbon-doped GaAs layer. In this example, trimethylgallium (TMGa) and arsine (AsH ₃ ) were used as Ga and As raw materials, and carbon tetrachloride (CCl ₄ ) was used as a carbon source. In this case, the flow rate of CCl ₄ was kept constant. Growth temperature is about 600
℃.

As a result of an experimental study conducted by the inventor, the carrier concentration sharply decreases in the [011] direction as the substrate is turned off, whereas the carrier concentration does not decrease in the [0 bar 11] direction. I found it. In this phenomenon, since C atoms form bonds with Ga atoms in the GaAs crystal and become p-type impurities, a conventional tilted orientation ([011] direction) substrate in which only Ga atoms are arranged in the surface step was used. In this case, the dissociation of the C raw material from the substrate surface is promoted and the uptake efficiency is reduced, whereas the conventional method [0 bar 1
In the substrate slightly tilted in the 1] direction, As is arranged in the step, so that the dissociation of the C raw material from the substrate surface is not promoted, and it is presumed that this is because the carrier concentration does not decrease. It

FIG. 2 shows the dependence of the current gain on the off-substrate angle when the present invention is applied to AlGaAs / GaAs HBT having a base layer doped with carbon. As can be seen from the figure, the current gain, that is, the minority carrier lifetime in the base layer is significantly improved by turning off the substrate regardless of the tilt direction. However, the carrier concentration of the base layer is [0 bar 1 as shown in FIG.
In the case of 1], since it is kept constant, the carrier concentration does not decrease and the current gain is improved. On the other hand, in the case of the off azimuth [011], as shown in FIG. 1, the carrier concentration of the base layer is reduced to about 1/2 or less as compared with the case of the off angle of 0 degree ((100) plane). The resistance is high and the high frequency characteristics of the device are poor.

Conventionally, the improvement of crystal quality by the slightly inclined substrate is
It has been thought to be due to a decrease in the amount of residual impurities (eg, oxygen that becomes a recombination center in GaAs) in the crystal, but it is clear from the fact that there is no azimuth dependence in the improvement of the current gain. The improvement is due to the reduction of the density such as defects peculiar to the crystal, and in the growth temperature range of the present invention, [0
There is no influence such as an increase in residual impurity concentration due to tilting in the direction of bar 11].

The inventors of the present invention have conducted a careful study on the assumption that the above effects have a deep correlation with the off orientation, angle, and growth temperature of the substrate. As a result, this tendency shows that the plane orientation of the substrate is the (100) plane. From the plane equivalent to this, it was confirmed that the growth temperature was about 580 ° C. or higher in the [0 bar 11] direction or the equivalent direction to the range of about 1 ° to about 10 °.

That is, in the above-mentioned embodiment, the off orientation of the substrate is set in the range of about 1 degree to about 10 degrees, but if the off orientation is less than about 1 degree, the effect of the present invention cannot be sufficiently obtained. On the other hand, if it exceeds about 10 degrees, other high index crystal planes appear, asymmetries such as various physical property constants and etching shapes appear, and the cleavage plane cannot be used. Although the growth temperature of the carbon-added layer is set to about 580 ° C. or higher, if the temperature is increased to about 700 ° C. or higher, a sufficiently high carrier concentration cannot be obtained or the growth itself becomes difficult. If the growth temperature is lowered to, for example, about 500 ° C. or lower, problems such as deterioration of crystal quality occur. Therefore, although the effect can be obtained qualitatively even below these regions, the orientation of the substrate is set in the range of about 1 ° to about 10 °, and the growth temperature is set at about 580.
A remarkable effect was obtained when the temperature was set to ℃ or higher.

Although CCl ₄ was used as the carbon raw material in the above-mentioned examples, other methods using TMGa, trimethylarsine (TMAs), trimethylaluminum (TMAl), CBr ₄ (carbon tetrabromide) were also used. The same effect can be obtained by a method using, for example. Also, although an example in the case of GaAs as a semiconductor layer to be grown, a similar effect is _{Al x Ga y In 1-xy} As (0 ≦ x ≦ 1,0 ≦ y
≦ 1) or GaAs _x Sb _1-x (0 ≦ x ≦ 1). Further, although the case of the HBT has been described in the present embodiment, the present invention can be applied to various elements such as a resonance tunnel element, a laser diode, an LED, a solar cell and the like.

[0015]

As described above, according to the present invention,
When growing a semiconductor laminated structure including a layer to which carbon is added as an impurity, there is no decrease in carrier concentration, crystal quality can be improved, and characteristics of various devices can be improved. can get. In addition, by using a tilted substrate with a specific range of orientation and setting the growth temperature in a specific range, it is possible to achieve extremely excellent effects such as high quality crystal growth without inhibiting the incorporation of carbon impurities. can get.

[Brief description of drawings]

FIG. 1 shows the off-angle dependence of carrier concentration according to an embodiment in which the vapor phase growth method for a compound semiconductor according to the present invention is applied to the crystal growth of a carbon-doped GaAs layer, where the off directions are [0 bar 11] and [011]. It is the figure which compared and showed about the case.

2 is a graph showing the carbon-doped GaAs layer of FIG.
The off-angle dependence of the current gain when applied to the base layer of GaAs HBT shows that [0 bar 11] and [0
11] is a diagram showing a comparison in the case of [11].

Claims (3)

[Claims] 1. A vapor phase growth method of a compound semiconductor having a laminated structure including at least one semiconductor layer to which carbon is added as an impurity on a substrate, wherein the plane orientation of the substrate is (100) plane or this (10) plane.
A method for vapor phase growth of a compound semiconductor, which comprises performing crystal growth using an off-substrate tilted from a plane equivalent to the (0) plane to a [0 bar 11] direction or a direction equivalent to this [0 bar 11] direction. 2. A vapor phase growth method of a compound semiconductor having a laminated structure including at least one semiconductor layer to which carbon is added as an impurity on a substrate, wherein the plane orientation of the substrate is (100) plane or this (10) plane.
0) surface is inclined in the [0 bar 11] direction or a direction equivalent to this [0 bar 11] direction within a range of 1 to 10 degrees, and the growth temperature of the carbon-added layer is 580 ° C. or more. A method for vapor phase growth of compound semiconductors, characterized in that crystal growth is performed by setting the above. 3. An apparatus according to claim 1 or claim 2, the semiconductor layer _{Al x Ga y In 1-xy} As (0 ≦ x ≦ 1,0
≦ y ≦ 1) The method for vapor phase growth of a compound semiconductor, characterized in that