MEASUREMENT OF THE TEMPERATURE DEPENDENCE OF MINORITY-CARRIER MOBILITY IN A TRANSISTOR-BASE REGION,

A method of measuring the temperature dependence of minority carriers in a transistor base is developed. The method is based on the observations that the short-circuit collector current of a transistor in a common-base configuration depends exponentially on the emitter voltage over several decades of collector current, and the temperature dependence of mobility has the empirical form mu is approximately equal to T to the a, where a, the temperature dependence parameter, is a constant. From these two observations a differential relation can be obtained which relates the parameter a to the extrapolated zero-temperature energy gap Vgo of the semiconductor, the emitter voltage Ve and the temperature derivative of the emitter voltage V sub e at a temperature T. From measurements of Ve, V sub e, T and the published value of Vgo, one can calculate the temperature-dependence parameter a from the differential relation. Calculations from the experimental data have yielded a weaker temperature dependence for the minority-carrier mobility in a transistor base than that in the bulk semiconductor. The weaker temperature dependence is correlated with the high dislocation count observed on the transistor. Author