SEDL / STP / STP712-EB / STP35135S

Measurement of Minority Carrier Lifetime in Silicon Crystals by the Photoconductive Decay Technique

Gerhard, AR
Senior engineers, Western Electric Co., Allentown, Pa.

Pearce, CW
Senior engineers, Western Electric Co., Allentown, Pa.

Pages: 10    Published: Jan 1980

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Abstract

A Nd:YAG laser was used to produce excess minority carriers in large-diameter silicon single crystals. The rate of decay of these carriers was then used as a measure of the minority carrier recombination lifetime. The high photon fluxes available from the laser made possible measurements on material of medium resistivity, generally not measureable with traditional instrumentation. The present apparatus includes: a laser light source modulated electronically, a low-noise preamplifier, and sampling and averaging instrumentation. This permits resulting signals as low as a few microvolts to be easily read and interpreted. The system has measured material ranging in lifetime from 50 to 4000 μs and represents a state-of-the-art approach to photoconductive decay measurements.