  We observe a series of discontinuities in the above gap current/voltage
characteristics of highly transmissive Nb/Si superconductor/semiconductor
interfaces. The bias at which each switch occurs decreases in quantized steps
as a function of temperature and magnetic field. The observed step-size is the
same for both dependencies. We propose that the steps correspond to
supercurrent quantization through granular Josephson junctions formed near the
interface.
