High-field current fluctuations in n-type germanium

Abstract

The work reported here is an investigation of high-frequency electrical noise in n-type germanium at 77 K under a high, pulsed electric field.Previous studies of nonequilibrium noise were made of the fluctuating current normal to the electric field, in an investigation of the thermal component of the hot-electron velocity distribution, whereas in this work, the current fluctuations in the field direction are studied, with no attempt made to isolate the thermal contribution.The spectrum of the current fluctuations is taken as uniform over the range from 30 to 70 MHz, on the basis of the measurements made at these two frequencies, so that effects of carrier population fluctuations due to generation–recombination and trapping could be presumed to be small.The dominant feature of the results is the anisotropy of the noise temperature, which was interpreted as due principally to fluctuations in the [Formula: see text] valley populations, when valley drift velocities are unequal. For equal valley drift velocities, only the thermal component is present.