Electron Multiplication in Silicon and Germanium

Abstract

Electron multiplication in silicon and germanium has been studied in the high fields of wide $p\ensuremath{-}n$ junctions for voltages in the prebreakdown region. Multiplication factors as high as eighteen have been observed at room temperature. Carriers injected by light, alpha particles, or thermal-generation are multiplied in the same manner. The time required for the multiplication process is less than 2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ second. Approximately equal multiplication factors are obtained for injected electrons and injected holes. The multiplication increases rapidly as "breakdown voltage" is approached. The data are well represented by ionization rates computed by conventional avalanche theory. In very narrow junctions, no observable multiplication occurs before Zener emission sets in, as previously reported. It is incidentally determined that the efficiency of ionization by alpha particles bombarding silicon is 3.6\ifmmode\pm\else\textpm\fi{}0.3 electron volts per electron-hole pair produced.