JPH11274086A - Method for growing iii-v compound semiconductor and heterojunction bipolar transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for growing a carbon-added III-V compound semiconductor layer and a heterojunction bipolar transistor that is capable of preventing elimination of a group V element from the carbon-added III-V compound semiconductor layer, when the growth is stopped after growing the carbon-added III-V compound semiconductor layer and prevent the inactivation of carbon in the carbon-added III-V compound semiconductor layer. SOLUTION: This method for growing III-V compound semiconductor includes a process, where at least a carbon-added III-V compound semiconductor layer is formed on a semiconductor substrate and the growth is stopped by providing an organic compound containing group V element and a carrier gas after growing the carbon-added III-V compound semiconductor. Since the hole carrier density of the base layer of the heterojunction bipolar transistor produced by this growth method can be improved, the maximum oscillation frequency can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a group III-V compound semiconductor using metal organic chemical vapor deposition and a heterojunction bipolar transistor manufactured by the method.

[0002]

2. Description of the Related Art Currently, GaAs-based heterojunction bipolar transistors, which are promising as ultrahigh-speed electronic device elements, are being actively developed. GaAs heterojunction bipolar transistors generally use n-type GaAs for the collector layer, p-type GaAs for the base layer, and n-type AlGaAs for the emitter layer.

However, a p-type GaAs base layer and n-type
When growing the type AlGaAs emitter layer, the optimum growth temperature of p-type GaAs as the base layer is different from the optimum growth temperature of n-type AlGaAs as the emitter layer. Therefore, it is necessary to grow the base layer and the emitter layer at different temperatures, and it is necessary to suspend the growth while changing the growth temperature after growing the base layer. For example, JP-A-9
Japanese Patent Application Publication No. 17737 describes a technique for growing a carbon-added semiconductor layer, suspending the growth while maintaining a substrate temperature of 500 ° C. to 600 ° C., and then growing another semiconductor layer.

In addition, by interrupting the growth between the base layer growth step and the emitter layer growth step, mixing of the base layer material gas and the emitter layer material gas is prevented.
Thereby, the interface between the base layer and the emitter layer becomes steep, and the performance of the manufactured HBT is improved. Therefore,
It is widely practiced to interrupt the growth between the growth of the base layer and the growth of the emitter layer.

[0005]

However, when the growth is interrupted, the growth is usually interrupted while maintaining the substrate temperature at 400 ° C. or higher. However, if the surface of the base layer is exposed at a substrate temperature of 400 ° C. or more after the growth of the GaAs base layer, arsenic is desorbed from the GaAs base layer. As a result, the quality of the base-emitter interface deteriorates.
This causes a decrease in the current amplification factor in the performance of T.

As a method of solving this problem, a method of continuing to supply AsH ₃ , which is an arsenic source gas, during growth interruption in order to prevent arsenic desorption, can be considered.

[0007] However, it is known that AsH ₃ generates a lot of active hydrogen when dissociated. Active hydrogen is a chemically active atom that readily bonds to atoms such as carbon. Therefore, when the base layer is made of a carbon-added semiconductor, active hydrogen is taken into the base layer, and carbon as a donor is combined with active hydrogen, thereby inactivating carbon and increasing the hole carrier concentration of the base layer. Was found to decrease.

On the other hand, in a high output current HBT for mobile communication, the hole carrier concentration in the base layer is 2 × 10 ¹⁹ cm ^−3.
The above is required, and a higher hole carrier concentration of 5 × 10 ¹⁹ cm ⁻³ or more is required for an HBT used for millimeter wave communication to be put into practical use in the future. However, generation of active hydrogen is a major obstacle to forming such a high-concentration carbon-added layer.

Accordingly, an object of the present invention is to provide a carbon-added III
-After growing the group V compound semiconductor layer, when performing the growth interruption,
Carbon addition I which can prevent desorption of a group V element from a carbon addition III-V compound semiconductor layer and prevent inactivation of carbon in the carbon addition III-V compound semiconductor layer
An object of the present invention is to provide a method for growing a II-V compound semiconductor layer and a heterojunction bipolar transistor.

[0010]

According to the method of growing a III-V compound semiconductor of the present invention, at least a carbon-added III-V compound semiconductor layer is formed on a semiconductor substrate, and the carbon-added III-V compound semiconductor layer is formed. After growing the semiconductor, the method includes a step of supplying an organic compound containing a group V element and a carrier gas to interrupt the growth.

Further, the carbon-added III-V compound semiconductor layer contains an As element, and the organic compound containing a Group V element is an organic arsenic compound containing a bond between arsenic and carbon. .

A particularly preferred organic arsenic compound is trimethylarsenic or triethylarsenic.

A heterojunction bipolar transistor according to the present invention is characterized by having a semiconductor laminated structure including a base layer and an emitter layer manufactured by the above-described growth method.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) In this embodiment, samples 1 to 3 show how the hole carrier concentration of the carbon-doped p-type semiconductor layer changes depending on the atmosphere during the growth interruption.
Three types of samples were prepared and examined.

First, on a semi-insulating GaAs substrate, trimethylgallium (TMGa) and trimethylarsenic (TMAs) are supplied as source gases at a substrate temperature of 590 ° C., a V / III ratio of 3.5, and a supply amount of a group III source gas. 1.4 sccm,
Carbon-added p-type GaAs at reactor pressure of 60 Torr
The layer is grown 0.5 μm.

Next, the sample 1 is kept at a substrate temperature of 590 ° C. for 5 minutes in an atmosphere of AsH ₃ and hydrogen gas as a carrier gas. Further, as a sample 2, a substrate temperature of 5
Keep tertiary butyl arsine (TBA) at 90 ° C.
s) and a hydrogen gas as a carrier gas for 5 minutes. Sample 3 is kept at 590 ° C. for 5 minutes in an atmosphere of trimethylarsine (TMAs) and hydrogen gas as a carrier gas. Thereafter, a non-doped AlGaAs layer as a cap layer is grown to a thickness of 0.05 μm on the carbon-doped p-type GaAs layer.

FIG. 1 shows the results of measuring the hole carrier concentration of each sample. As shown in FIG. 1, the sample 2 in which the growth was interrupted in an atmosphere of TBAs and hydrogen gas was A
The hole carrier concentration was higher than that of Sample 1 in which the growth was interrupted in an atmosphere of sH ₃ and hydrogen gas, and the inactivation of the added carbon could be suppressed. Further, the sample 3 in which the growth was interrupted in the atmosphere of TMAs and hydrogen gas had a higher hole carrier concentration than the sample 2 in which the growth was interrupted in the atmosphere of TBAs and hydrogen gas, and the added carbon was inactivated. Could be suppressed.

In this embodiment, TM gas is used as the group V source gas.
The case where As was used was taken up, but triethyl arsenic (T
Similar effects were obtained by using other raw materials containing a bond between arsenic and carbon, such as EAs).

(Embodiment 2) In the first embodiment, the substrate temperature at the time of the interruption of the growth is the same as the growth temperature of the carbon-added p-type semiconductor layer. Three kinds of samples 4 to 6 were prepared to examine how the hole carrier concentration of the carbon-doped p-type semiconductor layer changes depending on the atmosphere during the growth interruption when the growth temperature is higher than the growth temperature of the semiconductor layer. Was.

The structure of each sample, source gas, growth temperature, V /
A carbon-added p-type GaAs layer is formed in the same manner as in Example 1 with respect to the III ratio, the supply amount of the group III source gas, and the reactor internal pressure.

Next, as Sample 4, the substrate temperature is raised to 640 ° C., and the sample 4 is kept for 5 minutes in an atmosphere of AsH ₃ and hydrogen gas as a carrier gas. Further, as Sample 5, the substrate temperature is raised to 640 ° C., and the sample is kept in an atmosphere of tertiary butyl arsine (TBAs) and hydrogen gas as a carrier gas for 5 minutes. Further, as the sample 6, the substrate temperature 64
The temperature is raised to 0 ° C., and kept for 5 minutes in an atmosphere of trimethylarsine (TMAs) and hydrogen gas as a carrier gas. Thereafter, while keeping the substrate temperature at 640 ° C., a non-doped AlGaAs layer is grown as a cap layer to a thickness of 0.05 μm on the carbon-doped p-type GaAs layer.

FIG. 2 shows the results of measuring the hole carrier concentration of each sample. As shown in FIG. 2, Sample 5 in which the growth was interrupted in an atmosphere of TBAs and hydrogen gas was A
The hole carrier concentration was higher than that of Sample 4 in which the growth was interrupted in an atmosphere of sH ₃ and hydrogen gas, the inactivation of the added carbon could be suppressed, and the growth was at a higher substrate temperature than the carbon-doped p-type GaAs layer. The interruption can further activate the added carbon. Further, the sample 6 in which the growth was interrupted in the atmosphere of TMAs and hydrogen gas had a higher hole carrier concentration than the sample 5 in which the growth was interrupted in the atmosphere of TBAs and hydrogen gas, and the added carbon was inactivated. Can be suppressed, and the added carbon can be further activated by interrupting the growth at a substrate temperature higher than that of the carbon-doped p-type GaAs layer.

In this embodiment, TM gas is used as the group V source gas.
The case where As was used was taken up, but triethyl arsenic (T
Similar effects were obtained by using other raw materials containing a bond between arsenic and carbon, such as EAs).

(Embodiment 3) In this embodiment, the emitter Al
In a GaAs / base GaAs HBT, the substrate temperature when the growth of the base layer and the emitter layer was interrupted was raised to 640 ° C., and two types of HBTs of samples HBT1 and HBT2 having different atmospheres at that time were produced. Maximum oscillation frequency (fm
ax) was measured.

FIG. 5 is a sectional view of the HBT manufactured in this embodiment. On a semi-insulating GaAs substrate 1, an n-type GaAs collector contact layer 2 having an electron carrier concentration of 5 × 10 ¹⁸ cm ⁻³ is formed to a thickness of 0.5 μm and an electron carrier concentration of 2 × 10 ¹⁶
cm ⁻³ n-type GaAs collector layer 3 having a thickness of 0.7 μm;
A p-type GaAs base layer 4 having a hole carrier concentration of 2 × 10 ¹⁹ cm ⁻³ is formed to a thickness of 0.1 μm and an electron carrier concentration of 5 × 10 ¹⁹
MOCVD using an n-type Al _0.3 Ga _0.7 As emitter layer 5 of ¹⁷ cm ^-3 with a thickness of 0.1 μm and an n-type GaAs emitter contact layer 6 with an electron carrier concentration of 5 × 10 ¹⁸ cm ^-3 with a thickness of 0.2 μm An HBT is manufactured using a wafer obtained by epitaxial growth according to the method.

The p-type GaAs base layer 4 is grown at a growth temperature of 590 ° C., a V / III ratio of 3.5, a group III source gas of 1.4 sccm, and a reactor internal pressure of 60 Torr.
Grown in. Next, as the sample HBT1, the substrate temperature was set to 640 ° C. with the base-emitter interface 7 exposed on the surface.
And growth was interrupted for 5 minutes in an atmosphere of AsH ₃ and hydrogen gas. Further, as the sample HBT2, the substrate temperature was set to 640 ° C. with the base-emitter interface 7 exposed on the surface.
And growth was interrupted for 5 minutes in an atmosphere of TMAs and hydrogen gas.

Then, for both samples HBT1 and HBT2,
Al _0.3 Ga _0.7 As while keeping the substrate temperature at 640 ° C.
An emitter layer is grown, and then the emitter width is 2.4 μm
An HBT is prepared as follows.

FIG. 3 shows the result of measuring the maximum oscillation frequency of the HBT of each sample thus manufactured. Samples HBT2 which was grown interrupted in an atmosphere of TMAs and hydrogen gas as shown in FIG. 3, the maximum oscillation frequency is greater than the sample HBT1 which was grown interrupted in an atmosphere of AsH ₃ and hydrogen gas. This sample HBT2 which was grown interrupted in an atmosphere of TMAs and hydrogen gas from AsH ₃ and the sample HBT1 which was grown interrupted in an atmosphere of hydrogen gas, in order to hole carrier concentration of the base could be increased It is believed that there is. In order to further increase the number of hole carriers in the base layer, as in the second embodiment, by increasing the substrate temperature during the growth interruption with the base-emitter interface 7 exposed on the surface, the carbon in the base layer is further increased. The activation rate can be improved. Even in this case,
Samples were grown interrupted in an atmosphere of TMAs and hydrogen gas HBT2, the maximum oscillation frequency than AsH ₃ and the sample HBT1 which was grown interrupted in an atmosphere of hydrogen gas is increased.

(Embodiment 4) In this embodiment, the emitter In
In an HBT made of GaP / base GaAs, the substrate temperature when the growth of the base layer and the emitter layer is interrupted is set to 590 ° C.
, And two types of HBTs having different atmospheres at that time were prepared, and the maximum oscillation frequency (fmax) of each HBT was measured.

FIG. 6 is a sectional view of the HBT manufactured in this embodiment. An n-type GaAs collector contact layer 9 having an electron carrier concentration of 5 × 10 ¹⁸ cm ⁻³ is formed on a semi-insulating GaAs substrate 8 to a thickness of 0.5 μm and an electron carrier concentration of 2 × 10 ^16.
film thickness n-type GaAs collector layer 10 cm ^-3 0.7 .mu.m
m, p-type GaAs having a hole carrier concentration of 2 × 10 ¹⁹ cm ⁻³
The s base layer 11 has a thickness of 0.1 μm and an electron carrier concentration of 5
× 10 ¹⁷ cm ⁻³ n-type In _0.5 Ga _0.5 P emitter layer 12
With a thickness of 0.1 μm and an electron carrier concentration of 5 × 10 ¹⁸ cm ⁻³
N-type GaAs emitter contact layer 13 having a thickness of 0.2
An HBT is manufactured by using wafers obtained by epitaxial growth by the MOCVD method sequentially with a thickness of μm.

The p-type GaAs base layer 11 is grown at a growth temperature of 590 ° C., a V / III ratio of 3.5, a group III source gas of 1.4 sccm, and a reactor internal pressure of 60 Torr.
g. Next, as a sample HBT3, with the base-emitter interface 14 exposed on the surface, the substrate temperature was set to 59.
While maintaining the temperature at 0 ° C., the growth was suspended for 5 minutes in an atmosphere of AsH ₃ and hydrogen gas. Also, as a sample HBT4,
The growth was interrupted for 5 minutes in an atmosphere of TMAs and hydrogen gas while maintaining the substrate temperature at 590 ° C. with the base-emitter interface 14 exposed on the surface.

Then, for both samples HBT3 and HBT4,
While maintaining the substrate temperature at 590 ° C., the n-type In _0.5 Ga
_{A 0.5} P emitter layer is grown to produce an HBT having an emitter width of 2.4 μm.

FIG. 4 shows the result of measuring the maximum oscillation frequency of the HBT of each sample thus manufactured. Samples HBT4 which was grown interrupted in an atmosphere of TMAs and hydrogen gas as shown in FIG. 4, the maximum oscillation frequency is greater than the sample HBT3 which was grown interrupted in an atmosphere of AsH ₃ and hydrogen gas. This sample HBT4 which was grown interrupted in an atmosphere of TMAs and hydrogen gas from AsH ₃ and the sample HBT3 which was grown interrupted in an atmosphere of hydrogen gas, in order to hole carrier concentration of the base could be increased It is believed that there is. In order to further increase the hole carrier concentration of the base layer, as in the second embodiment, a heat treatment is performed by increasing the substrate temperature during the growth interruption while the base-emitter interface 14 is exposed on the surface. Further, the carbon activation rate of the base layer can be improved. In this case, the sample HBT4 which was grown interrupted in an atmosphere of TMAs and hydrogen gas, the maximum oscillation frequency than AsH ₃ and the sample HBT3 which was grown interrupted in an atmosphere of hydrogen gas is increased.

[0034]

According to the present invention, it is possible to prevent the desorption of a group V element from a carbon-added III-V compound semiconductor layer when the growth is interrupted after the growth of the carbon-added III-V compound semiconductor layer. And inactivation of the added carbon can be prevented. This allows the carbon addition III-V
The hole carrier concentration of the group III compound semiconductor layer can be increased. In addition, the HBT produced by the growth method of the present invention
Can increase the hole carrier concentration of the base layer, so that the maximum oscillation frequency can be increased.

[Brief description of the drawings]

FIG. 1: Carbon-doped Ga with different atmosphere during growth interruption
It is a figure showing the result of having measured the hole carrier density of an As layer.

FIG. 2 is a diagram showing the results of measuring the hole carrier concentration of a carbon-doped GaAs layer in which the atmosphere during the growth interruption was changed when the substrate temperature during the growth interruption was higher than that of the carbon-doped GaAs layer.

[FIG. 3] HB prepared by changing the atmosphere during the growth interruption
FIG. 9 is a diagram showing a result of measuring a maximum oscillation frequency of T.

FIG. 4 is a diagram showing the results of measuring the maximum oscillation frequency of an HBT in which the atmosphere during the growth interruption was changed.

FIG. 5 shows base GaAs / grown by the growth method of the present invention.
FIG. 3 is a diagram showing a structure of an HBT made of an emitter AlGaAs.

FIG. 6 shows the base GaAs /
FIG. 3 is a diagram showing a structure of an HBT made of an emitter InGaP.

[Explanation of symbols]

1,8 Semi-insulating GaAs substrate 2,9 n-type GaAs collector contact layer 3,10 n-type GaAs collector layer 4,11 p-type GaAs base layer 5 n-type Al _0.3 Ga _0.7 As emitter layer 6,13 n-type GaAs emitter Contact layer 7, 14 Base-emitter interface 12 n-type In _0.5 Ga _0.5 P emitter layer

Claims (4)

[Claims] 1. A semiconductor substrate comprising at least a carbon-doped I
Forming a group II-V compound semiconductor layer,
A method for growing a group III-V compound semiconductor, comprising a step of supplying an organic compound containing a group V element and a carrier gas to interrupt the growth after growing the group IV compound semiconductor. 2. The carbon-added III-V compound semiconductor layer contains an As element, and the organic compound containing a Group V element is an organic arsenic compound containing a bond between arsenic and carbon. A method for growing a group III-V compound semiconductor according to claim 1. 3. The organic arsenic compound is trimethyl arsenic or triethyl arsenic.
3. The method for growing a group III-V compound semiconductor according to item 1. 4. A hetero-junction bipolar transistor having a semiconductor multilayer structure including a base layer and an emitter layer manufactured by the growth method according to claim 1.