Multilayer vapor-phase epitaxial silicon millimeter-wave IMPATT diodes

A new procedure has been developed for fabricating small-area silicon avalanche diodes directly on a plated copper heat sink. The process incorporates multilayer vapor-phase epitaxially grown silicon and a preferential electrochemical etching technique to fabricate thin uniform silicon films; 6 µ thick films on 2-cm diameter wafers have been obtained reproducibly with little difficulty. Inverted mesa diodes 30-40 µ in diameter have been formed by etching through the unmasked area of the thinned silicon wafer. Implementation of this technology has resulted in single drift region p⁺-n-n⁺diodes that generate over ¼ W CW power with 6-percent efficiency at 60 GHz.