Power diodes for cryogenic operation

We have investigated and developed Ge power diodes for operation at cryogenic temperatures. We first examined commercial Ge power diodes and found that they were capable of satisfactory operation down to deep cryogenic temperatures, /spl sim/20 K (-253/spl deg/C), and that their forward voltage was considerably lower than that of Si power diodes. However, their reverse breakdown voltage was lower than we desired. We then designed and fabricated Ge power diodes (nominal 10-A forward current) for cryogenic temperature operation. A primary objective was to improve their reverse characteristics. We have achieved reverse breakdown voltages as high as 400 V over the temperature range from room temperature down to /spl sim/4 K (-269/spl deg/C).