A Germanium Field-Effect Transistors Made from a High-Purity Substrate

Field effect transistors have been fabricated on high-purity germanium substrates using low temperature technology. The aim of this work is to preserve the low density of trapping centers in high-quality starting material by low temperature (<350°C) processing. The use of germanium promises to eliminate some of the traps which cause generation-recombination noise in silicon field effect transistors (FET´s) at low temperatures. Typically, the transconductance (gm) in the germanium FET´s is 10 mA/V and the gate leakage can be less than 10-12 A. Our present devices exhibit a large 1/f noise component and most of this noise must be eliminated if they are to be competitive with silicon FET´s commonly used in high-resolution nuclear spectrometers.