Field-Induced Conductivity Changes in Germanium

Variations in the conductance of a germanium filament due to an electric field normal to the surface were measured for fields up to ${10}^5$ volts/cm. Observation of a minimum in the conductance curve makes it possible to calculate charge in surface states as a function of surface potential. Information of this sort obtained with several gaseous ambients is compared with the Brattain-Bardeen observations on contact potential. Measurements as a function of temperature down to 170°K give information about properties of "fast" surface states. Phase shift loops observed at frequencies around a kilocycle are interpreted in terms of minority carrier lifetime. Phase shift loops at low temperatures are believed to be due to traps.