The forward and reverse current-voltage characteristics and reverse-biased capacitance are described for the nZnSo-p+ Ge emitter-base diodes of heterojunction transistors. The forward diode current flow involves essentially electron injection into the Go together with loss-mechanisms of recombination of injected electrons through interface states and, probably, electron capture into ZnSo traps followed by tunnelling into interface states. In the junctions that have been fabricated, the current-voltage characteristics are dominated by the high resistivity bulk ZnSo in series with the junction, resulting in space-charge-limited flow. The reverse junction characteristics demonstrate semi-saturation, avalanche multiplication, and negative resistance. The junction capacitance is strongly frequency dependent duo to the presence of relatively deep traps, and both abrupt and linearly graded junctions have boon observed, depending on the growth technique.