Radiation Effects on the Microwave Properties of GaAs MESFETs.
Final technical rept. 1 Apr 78-30 Jun 79,
RENSSELAER POLYTECHNIC INST TROY NY DEPT OF ELECTRICAL AND SYSTEMS ENGINEERING
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The effect of fast neutron and gamma irradiation on the electrical characteristics of low noise microwave GaAs MESFET amplifiers has been evaluated. The microwave amplifiers were realized on alumina microstrip using commercial devices mounted in a common source configuration. The changes in the noise figure and amplifier gain at S- and X-band were determined for neutron fluences between 3 x 10 to the 12th power to 1 x 10 to the 15th power nsq cm and for a gamma dose of 2 x 10 to the 7th power rads Si. The noise figure starts to be affected at 10 to the 14th power nsq cm and a large deterioration is observed at 1 x 10 to the 15th power nsq cm. The increase in noise figure is related to the decrease in transconductance and increase in the parasitic source resistance. The decrease in the amplifier gain at the high neutron fluence is due to a deterioration of the transconductance, source resistance and change in the gate to source and gate to drain capacitances. The low frequency noise increases with neutron radiation but not with gamma-radiation. The low frequency noise appears not to be correlated with the microwave noise. Gamma irradiation increases the noise figure at a dose of 2 x 10 to the 7th power rads Si without affecting the signal characteristics of the device. It appears that Gamma-radiation produces levels which respond at microwave frequencies.
- Electrical and Electronic Equipment
- Solid State Physics