Effects of neutron irradiation on GaAs/AlGaAs heterojunction bipolar transistors

The effects of neutron irradiation on 3- mu m-emitter, self-aligned-base, ohmic metal GaAs/AlGaAs heterojunction bipolar transistors and ICs based on molecular beam epitaxy have been experimentally and analytically investigated at fluence levels up to 1.3*10/sup 14/ n/cm/sup 2/. Devices with high DC current gain, beta , exhibited higher sensitivity to neutron irradiation than those with low beta . At 1.3*10/sup 14/ n/cm/sup 2/, DC beta was degraded by 25% for high- beta devices and by 7% for low- beta devices. Parasitic base current components such as the emitter edge recombination seem to be the key factor determining the neutron sensitivity. The functional dependence of beta on neutron fluence seems to follow the Messenger-Spratt relation, manifested by a linear increase of the base current with fluence. No deterioration was seen either in transistor RF characteristic or in digital circuit high-speed performance due to neutron irradiation up to a fluence of 1.3*10/sup 14/ n/cm/sup 2/.<
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