Gold-Epitaxial Silicon High-Frequency Diodes

The metal-semiconductor rectifying contact in a variety of configurations called "point contact" has long been used for microwave rectification and amplification. This investigation shows that metal-semiconductor diodes can be designed and fabricated by large-area techniques with speeds adequate for application as fractional nanosecond switches or microwave mixers. In particular, a gold n-type silicon contact will be considered here. An estimate of the response time can be obtained from a calculation of the transit time of electrons through the space charge region and the RC time. The series resistance and capacitance of the diode are made small by using an epitaxial structure. Since the hole injection in these diodes at low currents is negligibly small, the response time can be independent of hole lifetime. In what follows, design of these diodes will be discussed, and the predictions of the preliminary design will be compared with experiment. 225 226 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1964