JPH0327122B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to improving the radiation resistance of the GaAs FET in a semiconductor device consisting of a GaAs FET and a resistor divider circuit for applying a gate voltage to the GaAs FET. More specifically, the present invention relates to a method for improving the radiation resistance of a circuit using GaAs FETs by improving the bias circuit of GaAs FETs.

[Prior art]

GaAs FET is a high-frequency transistor that operates in the UHF band, microwave band, and millimeter wave band.
It is used in satellite communications, radar, and other high-frequency band equipment. Among these applications, they are often used in environments with strong radiation, such as outer space. When used in such an environment, resistance to radiation becomes important for the reliability of the device.

Figure 2 shows a semiconductor device using the conventional general bias application method.
FET, the source 1a of the FET 1 is grounded,
A positive voltage (Vd) is applied to the drain 1b, and a negative voltage (-Vg) is applied to the gate 1c.

FIG. 3 shows the drain 1b of the low-noise amplification GaAs FET in the conventional semiconductor device shown in FIG.
Applying constant voltages Vd and -Vg to the gate 1c, respectively,
This figure shows the change in static characteristics when the FET is irradiated with gamma rays in this state. In the figure, it can be seen that as the γ-ray irradiation dose increases, the drain saturation current (Idss), pinch-off voltage (Vp), and transconductance (gm) all decrease.
In particular, the drain saturation current Idss was halved by irradiation with γ-rays of 1×10 ⁹ rad, and the change was remarkable.

Figure 4 shows GaAs under the same conditions as above.
This shows changes in the high frequency characteristics of FET.
Figure 4 a shows the noise figure (NF), and Figure 4 b shows the gain (Ga).
In the figure, as the irradiation dose increases, NF increases and Ga decreases.
It can be seen that, like the static characteristics, the high frequency characteristics are also degraded by radiation irradiation.

[Problem that the invention seeks to solve]

In this way, the characteristics of GaAs FETs change when exposed to radiation, and for this reason, the characteristics of conventional semiconductor devices using GaAs FETs that are used in environments where radiation exists will change (or deteriorate). , which was a practical problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor device whose characteristics are less likely to change due to radiation.

[Means for solving problems]

The present invention provides a semiconductor device including a GaAs FET and a resistance dividing circuit for applying a voltage to its gate electrode, in which at least one of the resistors of the resistance dividing circuit is formed using GaAs.

[Effect]

In the present invention, when irradiated with radiation, the bias point of the gate is changed so that, for example, GaAs
Changes in electrical characteristics of FET due to radiation are reduced.

〔Example〕

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

FIG. 1 shows an embodiment of the invention. In the figure, the same reference numerals as in Figure 2 indicate the same or equivalent parts, and 2 is a resistance divider for dividing the gate bias voltage (-Vg) by two resistors R1 and R2 and supplying it to the gate electrode 1c of the GaAs FET. It is a circuit.
At this time, the gate voltage applied to the GaAs FET is −Vg
×R2/(R1+R2)=-Vg0. By the way, such a biasing method using the resistor divider circuit 2 has been generally performed in the past, but the feature of the present invention is that both or one of the resistors R1 and R2 is made of GaAs, and in this embodiment, Resistor R2 is an ordinary resistor such as a metal film resistor, and resistor R1 is
Made of GaAs.

Next, the effects will be explained.

As the radiation dose increases, the value of resistor R1 increases, but on the other hand, the value of resistor R2 hardly changes, so as a result, the voltage division ratio R2/(R1+R2) decreases, and the bias becomes shallower and is applied to gate 1c. The voltage decreases and the bias point moves in the direction of increasing drain current. At this time, as can be seen from Figure 3, the drain saturation current increases due to radiation.
Idss is about to decrease, but the effect of decreasing Idss due to this radiation and the increase in drain current due to the change in the bias point act to cancel each other out.

Therefore, take appropriate values of resistors R1 and R2 and -Vg
By appropriately selecting the value of , changes in drain saturation current Idss can be reduced. Fifth
The figure shows the results obtained using the bias method according to the above example.
In GaAs FET, the drain current is approximately 10m
Change in high frequency characteristics when A is set constant. This is what was shown. As is clear from this figure, although the noise figure (NF) deteriorates as the radiation dose increases, the gain (Ga) no longer decreases and remains almost constant, which is compensated for.

In this way, in this embodiment, the electrical characteristics, especially the gain, of the GaAs FET circuit can be stabilized against radiation.

In the above embodiment, an example of stabilizing the gain was shown, but in the present invention, the noise figure (NF) can also be compensated by appropriately selecting the resistors R1 and R2. In addition, in the above embodiment, only the resistor R1 was formed of GaAs, but both resistors R1 and R2 were formed of GaAs.
A similar effect can also be obtained by forming GaAs and varying the carrier concentration in the portions where R1 and R2 are formed.

〔Effect of the invention〕

As described above, according to the semiconductor device according to the present invention, at least one of the resistors of the resistor divider circuit is
Since it is formed using GaAs, the bias point of the gate can be changed by irradiation with radiation.
As a result, it has the effect of reducing changes in characteristics of GaAs FETs due to radiation, for example.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a semiconductor device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional semiconductor device, and FIG. 3 is a characteristic diagram showing changes in static characteristics of a GaAs FET.
Figure 4 a and b are characteristic diagrams showing changes in high frequency characteristics;
FIG. 5 is a characteristic diagram for explaining the effects of the above embodiment. 1...GaAs FET, 1c...gate, 2...
Resistance dividing circuit, R1, R2...first and second dividing resistors.

Claims (1)

[Claims] 1. A semiconductor device including a GaAs FET and a resistance divider circuit for dividing a constant voltage by resistance to obtain a gate voltage of the GaAs FET, wherein at least one of the resistors of the resistance divider circuit is A semiconductor device characterized in that it is formed using GaAs. 2 The GaAs FET mentioned above is n-type, and the resistance dividing circuit consists of a first and second dividing resistor connected in series between the negative power supply and the ground, and the GaAs FET is used in the first dividing resistor. A semiconductor device according to claim 1, characterized in that: