JP3408419B2 - Method of growing III-V compound semiconductor and heterojunction bipolar transistor - Google Patents

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 a metal organic chemical vapor deposition method 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 ultrafast electronic device elements, are being actively developed. A GaAs heterojunction bipolar transistor generally uses n-type GaAs for the collector layer, p-type GaAs for the base layer, and n-type AlGaAs for the emitter layer.

However, the p-type GaAs base layer and the n-type
When growing a p-type AlGaAs emitter layer, the optimum growth temperature of p-type GaAs that is a base layer and the optimum growth temperature of n-type AlGaAs that is an emitter layer are different. Therefore, it is necessary to grow the base layer and the emitter layer at different temperatures, and it is necessary to stop the growth after growing the base layer while changing the growth temperature. For example, JP-A-9
Japanese Patent Publication No. 17737 discloses a technique of growing a carbon-added semiconductor layer, holding a substrate temperature of 500 ° C. to 600 ° C. to stop the growth, and then growing another semiconductor layer.

Further, by interrupting the growth between the base layer growing step and the emitter layer growing step, it is possible to prevent the material gas of the base layer and the material gas of the emitter layer from being mixed.
This makes the interface between the base layer and the emitter layer steep and improves the performance of the HBT to be manufactured. Therefore,
It is common practice 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, it is usual to hold the substrate temperature of 400 ° C. or higher to interrupt the growth. However, if the surface of the base layer is exposed at a substrate temperature of 400 ° C. or higher after growing the GaAs base layer, there is a problem that arsenic is released from the GaAs base layer. This deteriorates the quality of the base-emitter interface.
This causes a decrease in current amplification factor in the performance of T.

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

However, AsH ₃ is known to generate a large amount of active hydrogen when dissociated. Active hydrogen is a chemically active atom that easily bonds with an atom such as carbon. Therefore, when the base layer is a carbon-added semiconductor, active hydrogen is taken into the base layer, carbon as a donor and active hydrogen are bonded, and as a result, carbon is inactivated and the hole carrier concentration of the base layer is increased. Was found to decrease.

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

The object of the present invention is therefore to add carbon III
When the growth of the group V compound semiconductor layer is stopped after the growth,
Carbon addition I capable of preventing the desorption of the group V element from the carbon-added III-V compound semiconductor layer and preventing the deactivation of carbon in the carbon-added III-V compound semiconductor layer
An object of the present invention is to obtain a II-V compound semiconductor layer growth method and a heterojunction bipolar transistor.

[0010]

According to the method for growing a III-V group compound semiconductor of the present invention, at least a carbon-doped III-V group compound semiconductor layer is formed on a semiconductor substrate. After the growth of the semiconductor layer, a step of supplying an organic compound containing a group V element and a carrier gas to suspend the growth is included. After the growth is suspended, n-type AlGaA
It is characterized by growing an s layer or an n-type InGaP layer .

Further , the substrate temperature at the time of the growth interruption is set to the growth temperature.
It is characterized by being made higher than the degree.

Further, the carbon-doped III-V group compound semiconductor layer contains an As element, and the organic compound containing the V group element is an organic arsenic compound containing a bond of arsenic and carbon. .

A particularly preferred organic arsenic compound is trimethylarsenic or triethylarsenic.

The heterojunction bipolar transistor of the present invention is characterized by having a semiconductor laminated structure including a base layer and an emitter layer manufactured by the above growth method.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) In this embodiment, three kinds of samples, Samples 1 to 3, were examined as to how the hole carrier concentration of the carbon-doped p-type semiconductor layer changes depending on the atmosphere during the growth interruption. Was produced and investigated.

First, trimethylgallium (TMGa) and trimethylarsenic (TMAs) are used as source gases on a semi-insulating GaAs substrate 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, as Sample 1, the substrate temperature is kept at 590 ° C. for 5 minutes in the atmosphere of AsH ₃ and hydrogen gas as a carrier gas. In addition, as the sample 2, the substrate temperature is 5
Tertiary butyl arsine (TBA
s) and a carrier gas of hydrogen gas for 5 minutes. Further, as the sample 3, the substrate temperature is kept at 590 ° C. for 5 minutes in an atmosphere of trimethylarsine (TMAs) and hydrogen gas which is a carrier gas. After that, 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.

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

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

Example 2 In Example 1, the substrate temperature at the time of growth interruption was set to be the same as the growth temperature of the carbon-doped p-type semiconductor layer, but in this Example, the substrate temperature at the time of growth interruption was set at the carbon-added p-type semiconductor layer. Three types of samples 4 to 6 were prepared and investigated to see how the hole carrier concentration of the carbon-doped p-type semiconductor layer changes depending on the atmosphere when the growth is suspended when the temperature is higher than the growth temperature of the type semiconductor layer. It was

Structure of each sample, source gas, growth temperature, V /
The III ratio, the supply amount of the group III source gas, and the reactor internal pressure are the same as in Example 1, and a carbon-doped p-type GaAs layer is formed.

Next, as a sample 4, the substrate temperature is raised to 640 ° C. and held for 5 minutes in an atmosphere of AsH ₃ and hydrogen gas which is a carrier gas. Further, as the sample 5, the substrate temperature is raised to 640 ° C. and held for 5 minutes in an atmosphere of tertiary butyl arsine (TBAs) and hydrogen gas which is a carrier gas. Further, as the sample 6, the substrate temperature 64
The temperature is raised to 0 ° C. and maintained for 5 minutes in an atmosphere of trimethylarsine (TMAs) and hydrogen gas which is a carrier gas. Then, while maintaining the substrate temperature at 640 ° C., 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.

The results of measuring the hole carrier concentration of each sample are shown in FIG. As shown in FIG. 2, the sample 5 in which the growth was suspended in the atmosphere of TBAs and hydrogen gas was A
The hole carrier concentration is higher than that of sample 4 in which the growth is suspended in the atmosphere of sH ₃ and hydrogen gas, the inactivation of the added carbon can be suppressed, and the growth is performed at a substrate temperature higher than that of the carbon-added p-type GaAs layer. By interrupting, the added carbon can be further activated. Further, the sample 6 suspended in the atmosphere of TMAs and hydrogen gas has a higher hole carrier concentration than the sample 5 suspended in the atmosphere of TBAs and hydrogen gas, and the added carbon is inactivated. Can be suppressed, and the added carbon can be further activated by suspending the growth at a substrate temperature higher than that of the carbon-added p-type GaAs layer.

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

Example 3 In this example, the emitter AlGaAs / base GaAs is used.
In the HBT, the substrate temperature at the time of interrupting the growth of the base layer and the emitter layer was raised to 640 ° C., and two types of HBTs, Samples HBT1 and 2 having different atmospheres at that time, were produced.
The maximum oscillation frequency (fmax) of BT was measured.

FIG. 5 shows a cross-sectional view of the HBT manufactured in this example. An n-type GaAs collector contact layer 2 having an electron carrier concentration of 5 × 10 ¹⁸ cm ⁻³ and a film thickness of 0.5 μm and an electron carrier concentration of 2 × 10 ^{16 is} formed on a semi-insulating GaAs substrate 1.
cm ⁻³ n-type GaAs collector layer 3 having a film 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 with a film thickness of 0.1 μm and an electron carrier concentration of 5 × 10.
^{A 17} cm ⁻³ n-type Al _0.3 Ga _0.7 As emitter layer 5 having a film thickness of 0.1 μm and an n-type GaAs emitter contact layer 6 having an electron carrier concentration of 5 × 10 ¹⁸ cm ⁻³ having a film thickness of 0.2 μm are sequentially formed by MOCVD. A HBT is manufactured using a wafer obtained by epitaxial growth by the method.

The growth conditions of the p-type GaAs base layer 4 are 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 sample HBT1, the substrate temperature was set to 640 ° C. with the base-emitter interface 7 appearing on the surface.
The temperature was raised to, and growth was suspended for 5 minutes in an atmosphere of AsH ₃ and hydrogen gas. As the sample HBT2, the substrate temperature was 640 ° C. with the base-emitter interface 7 appearing on the surface.
The temperature was raised to, and growth was suspended for 5 minutes in an atmosphere of TMAs and hydrogen gas.

After that, both the samples HBT1 and HBT2 were
Al _0.3 Ga _0.7 As while keeping the substrate temperature at 640 ° C
The emitter layer is grown, and then the emitter width is 2.4 μm.
A HBT that satisfies

FIG. 3 shows the result of measuring the maximum oscillation frequency of the HBT of each sample thus manufactured. As shown in FIG. 3, the sample HBT2 whose growth was interrupted in the atmosphere of TMAs and hydrogen gas had a larger maximum oscillation frequency than the sample HBT1 whose growth was interrupted in the atmosphere of AsH ₃ and hydrogen gas. This is because the sample HBT2, whose growth was interrupted in the atmosphere of TMAs and hydrogen gas, had a higher hole carrier concentration of the base than the sample HBT1 whose growth was interrupted in the atmosphere of AsH ₃ and hydrogen gas. It is believed that there is. In order to further increase the hole carriers in the base layer, the substrate temperature during the growth interruption is raised with the base-emitter interface 7 appearing on the surface in the same manner as in Example 2 to further increase the carbon in the base layer. The activation rate can be improved. Even in this case,
The maximum oscillating frequency of the sample HBT2 subjected to growth interruption in the atmosphere of TMAs and hydrogen gas was higher than that of the sample HBT1 subjected to growth interruption in the atmosphere of AsH ₃ and hydrogen gas.

(Embodiment 4) In this embodiment, in an HBT composed of emitter InGaP / base GaAs, the substrate temperature at the time of interrupting the growth of the base layer and the emitter layer is kept at 590 ° C., and a sample HBT3 having a different atmosphere at that time is held. 2 types of HBTs of
The maximum oscillation frequency (fmax) of each HBT was measured.

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

The growth conditions for the p-type GaAs base layer 11 are 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 Tor.
It was grown at r. Next, as the sample HBT3, the substrate temperature was set to 59 with the base-emitter interface 14 appearing on the surface.
The growth was suspended for 5 minutes in an atmosphere of AsH ₃ and hydrogen gas while maintaining the temperature at 0 ° C. Also, as the sample HBT4,
The growth was suspended for 5 minutes in an atmosphere of TMAs and hydrogen gas while the substrate temperature was kept at 590 ° C. with the base-emitter interface 14 exposed on the surface.

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

The result of measuring the maximum oscillation frequency of the HBT of each sample thus manufactured is shown in FIG. 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 in the base layer, the substrate temperature during the growth interruption is increased and heat treatment is performed in the state where the base-emitter interface 14 appears on the surface, as in the second embodiment. Further, the carbon activation rate of the base layer can be improved. Also in this case, the maximum oscillating frequency of the sample HBT4 subjected to growth interruption in the atmosphere of TMAs and hydrogen gas was higher than that of the sample HBT3 subjected to growth interruption in the atmosphere of AsH ₃ and hydrogen gas.

[0035]

According to the present invention, when the growth of the carbon-doped III-V group compound semiconductor layer is stopped after the growth, the desorption of the V-group element from the carbon-doped III-V group compound semiconductor layer is prevented. In addition, the deactivation of the added carbon can be prevented. By this, carbon addition III-V
The hole carrier concentration of the group compound semiconductor layer can be increased. In addition, the HBT produced by the growth method of the present invention
Since the hole carrier concentration of the base layer can be increased, the maximum oscillation frequency can be increased.

[Brief description of drawings]

FIG. 1 Carbon-added G with different atmosphere during growth interruption
It is a figure which shows the result of having measured the hole carrier concentration of an aAs 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 growth interruption was changed when the substrate temperature during growth interruption was higher than that of the carbon-doped GaAs layer.

FIG. 3 H produced by changing the atmosphere during growth interruption
It is a figure which shows the result of having measured the maximum oscillation frequency of BT.

FIG. 4 is a diagram showing the results of measuring the maximum oscillation frequency of HBTs with different atmospheres during growth interruption.

FIG. 5: Base GaAs produced by the growth method of the present invention
It is a figure which shows the structure of HBT which consists of / emitter AlGaAs.

FIG. 6 is a base GaAs produced by the growth method of the present invention.
It is a figure which shows the structure of HBT which consists of / 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 layers 7 and 14 Base-emitter interface 12 n-type In _0.5 Ga _0.5 P emitter layer

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Claims (5)

(57) [Claims] 1. At least carbon addition I on a semiconductor substrate.
Forming a II-V group compound semiconductor layer, and adding the carbon II
After the growth of the IV group compound semiconductor layer, a step of supplying an organic compound containing a group V element and a carrier gas to suspend the growth is included. After the growth is suspended, an n-type AlGaAs layer or
III- characterized by growing n-type InGaP layer
Method for growing group V compound semiconductor. 2. The substrate temperature when the growth is interrupted is defined as the growth temperature.
III in accordance with claim 1, characterized in that
-Group V compound semiconductor growth method. 3. The carbon-doped III-V group compound semiconductor layer contains an As element, and the organic compound containing the V group element is an organic arsenic compound containing a bond of arsenic and carbon. The method for growing a III-V compound semiconductor according to claim 1 or 2 . Wherein said organic arsenic compound according to claim 3, characterized in that the trimethyl arsenic or triethyl arsenic
The method for growing a group III-V compound semiconductor according to claim 1. 5. The heterojunction bipolar transistor characterized by having a semiconductor multilayer structure including a base layer and the emitter layer made of any of the growth method of claims 1 to 4.