CALCULATION AND ANALYSIS OF DC PARAMETERS IN SILICON HETEROJUNCTION BIPOLAR-TRANSISTORS WITH AMORPHOUS EMITTERS AT LOW-TEMPERATURES

The low temperature properties of silicon heterojunction bipolar trans istors with amorphous emitters are studied. It is indicated that the c urrent gain, H-FE, has a positive temperature coefficient and falls wi th increasing base concentration, N-B, at room temperature and low tem peratures, differing from conventional silicon bipolar transistors. H- FE increases with increasing applied voltage across the collector-base junction, because of the avalanche multiplication effect in the colle ctor-base junction at low temperatures. The collector current, I-C, in creases as N-B increases at low temperatures, which is entirely opposi te to the result at room temperature. It is finally concluded that the value of H-FE of this device at low temperatures is adequate for most applications.