LOW-TEMPERATURE CHARACTERISTICS OF ELECTRICAL PARAMETERS IN AMORPHOUSSI SI HETEROJUNCTION BIPOLAR-TRANSISTORS/

Measurement of the low temperature characteristics of current gain, H- FE, and cut-off frequency, f(T), in amorphous emitter silicon heteroju nction bipolar transistor is reported. The current gain, H-FE, has a p ositive temperature coefficient and falls with increasing base concent ration, N-B, at both room temperature and low temperatures. Because of the low-temperature avalanche multiplication effect in the collector- base junction, H-FE increases with increasing applied voltage, V-BC, a t low temperature. The cut-off frequency, f(T), has positive temperatu re coefficient at low current levels and negative temperature coeffici ent at high current levels. It is concluded finally that the value of H-FE of this device at low temperatures is adequate for most applicati ons.