Use of Infrared Absorption in Germanium to Determine Carrier Distributions for Injection and Extraction

Abstract

Measurements of the absorption of infrared radiation by the free carriers in germanium have been used to determine carrier distributions due to injection and extraction. The transverse distributions were found to agree with theory and have been used to determine surface recombination velocity. The longitudinal distributions may be put into four classifications. These are injection field-opposed, injection field-aided, extraction field-opposed and extraction field-aided. Some of these distributions have been studied in detail and have been correlated with the ambipolar carrier transport theory of van Roosbroeck. To do this it was necessary to take into account the change in carrier lifetime with carrier density, which was done according to the Shockley-Read theory. Good agreement was thus obtained between experiment and theory for longitudinal carrier distributions.