SURFACE CURRENTS IN INP/INGAAS HETEROJUNCTION BIPOLAR-TRANSISTORS PRODUCED BY PASSIVATION FILM FORMATION

The correlation between the passivation film formation for InP/InGaAs heterojunction bipolar transistors and transistor current-voltage (I-V) characteristics is investigated. The I-V characteristics vary significantly depending on the kind of passivation films. The major change in I-V characteristics is the increase in base current (I(b)), which implies the generation of an additional recombination process around the surface of the emitter-base junction. A change in collector current (I(c)) is also observed, indicating that the electron injection mechanism changed near the passivated semiconductor surface. These surface currents are produced by the interaction of the semiconductor surface with the passivation films. It is shown that these surface currents are greatly suppressed using a buffered hydrofluoric acid solution before the passivation film formation.