Generation Recombination Noise in Intrinsic and Near-Intrinsic Germanium Crystals

Abstract

Measurements are reported on noise in germaniumsingle crystals at temperatures between 300°K and 450°K. In this range the crystals were near‐intrinsic or intrinsic. The 1/f noise component was negligible in all cases above 1 kc providing the noise was measured between probes. The noise above thermal noise measured in this way could entirely be attributed to spontaneous fluctuations in generation and recombination of carriers. From the spectra lifetimes varying from 2 μsec for poorly etched crystals up to 100 μsec for the best etched crystals were found. The results are compared with the theory considering generation and recombination by means of direct transitions or via recombination centers located either in the bulk or at the surface. Very reasonable agreement is found in most cases. In some cases the spectrum falls off rather weakly at higher frequencies which indicates that the recombination centers do not lie at a single sharp energy in the forbidden gap but are distributed within a small range.