Excess Noise inn-Type Germanium

Abstract

An experimental examination of excess noise in $n$-type single crystal germanium has confirmed that the phenomenon behaves like conductivity modulation caused by carrier density fluctuations. The magnitude and frequency spectrum of the carrier density fluctuations, as measured by the Hall effect, yield good agreement with observed excess noise levels. Majority and minority carrier density fluctuations are correlated in such a way that the density varies percentagewise. It is shown experimentally that noise sources are distributed uniformly along the specimen length and that statistically independent volume elements are smaller than ${10}^{-5\mathrm{}}$ ${\mathrm{cm}}^3$. These results are independent of sample shape, resistivity, and surface treatment, which affect only the magnitude of the fluctuations. Results on samples with resistivities ranging from 1.5 to 35 ohm-centimeters show an increase in fluctuations with resistivity.