Active solid-state devices (e.g. – transistors – solid-state diode – Heterojunction device – Field effect transistor
Reexamination Certificate
2001-03-28
2002-12-31
Loke, Steven (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Heterojunction device
Field effect transistor
C257S194000, C257S200000, C438S167000, C438S172000, C438S285000
Reexamination Certificate
active
06501105
ABSTRACT:
BACKGROUD OF THE INVENTION
1. Field of the Invention
The present invention relates to a compound semiconductor device and, more particularly, a compound semiconductor device having a MESFET (Metal-Semiconductor FET).
2. Description of the Prior Art
In the power amplifier for the cellular phone base station, requests for the increase of the power supply voltage and the improvement of the power characteristic are increased in recent years, and thus the higher breakdown voltage is indispensable for the transistor employed in the power amplifier.
However, the MESFET having the GaAs channel layer is difficult to adapt to the increase of the power supply voltage since the GaAs channel layer is ready to be destroyed because of the electric field concentration, such MESFET is unsuitable for the power amplifier.
Therefore, the higher breakdown voltage of the MESFET is required.
In order to improve the breakdown voltage of the MESFET, as shown in
FIG. 1
, there is a structure in which the GaAs channel layer is replaced with the InGaP channel layer.
In
FIG. 1
, a buffer layer
102
made of AlGaAs is formed on a semiinsulating GaAs substrate
101
, and then a channel layer
103
made of n-type In
0.52
Ga
0.48
P and a barrier layer
104
made of undoped AlGaAs are formed in sequence on the buffer layer
102
.
Also, a contact layer
105
made of undoped GaAs is formed on the barrier layer
104
. An opening
105
a
for exposing the barrier layer
104
is formed in the contact layer
105
, and a gate electrode
106
is connected to the barrier layer
104
via the opening
105
a
. The gate electrode
106
and the barrier layer
104
are connected to each other to form Schottky junction.
In addition, a source electrode
107
and a drain electrode
108
are connected to the contact layer
105
on both sides of the gate electrode
106
. The n-type impurity is ion-implanted at a high concentration into the contact layer
105
located under the source electrode
107
and the drain electrode
108
. Accordingly, the source electrode
107
and the drain electrode
108
come into contact with the cap layer
105
to form ohmic-contact respectively.
The breakdown voltage of the above-mentioned MESFET having the InGaP channel layer is about 2 to 3 times higher than that of the MESFET having the GaAs channel layer.
As described above, since the MESFET whose channel layer is formed of InGaP has the high breakdown voltage rather than the prior art but the mobility in the channel layer
103
is low, the resistance is high and the mutual conductance (g
m
) is low. As a result, the gain is lowered rather than the prior art, and thus it is impossible to reap effectively the advantage such as the improvement of the breakdown voltage.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a compound semiconductor device having a transistor whose gain can be increased rather than the prior art.
The above subject can be overcome by forming the channel layer of the MESFET by InGaPSb.
Since the MESFET having the channel layer formed of InGaPSb make it possible to reduce the sheet resistance by using the small threshold voltage rather than the MESFET in the prior art, the mutual conductance and the gain of the MESFET can be increased without the reduction in the breakdown voltage.
REFERENCES:
patent: 5504353 (1996-04-01), Kuzuhara
patent: 5767539 (1998-06-01), Onda
patent: 5945695 (1999-08-01), Takikawa
patent: 6232624 (2001-05-01), Matloubian et al.
patent: 6-236898 (1994-08-01), None
patent: 7-335867 (1995-12-01), None
J.K. Shurtleff et al. U.S.A. Band-gap control of GalnP using Sb as a surfactant Applied Physics Letters vol. 75, No. 13, Sep. 27, 1999, pp. 1914-1916.
Armstrong Westerman & Hattori, LLP
Fujitsu Limited
Kang Donghee
Loke Steven
LandOfFree
Compound semiconductor device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Compound semiconductor device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compound semiconductor device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2919651