Recombination of Excess Carriers in Semiconductors

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The recombination of excess carriers in semiconductors is discussed on the basis of a model in which the recombination occurs through multiple-levels. The theory is extended to apply to germanium. The dependence of carrier lifetime on temperature in most of pure n -type germanium samples can be explained by introducing two sets of traps, recombination centers ( E C - E r =0.30eV) and hole trapping centers ( E t - E V =0.30eV), in our temperature range. However, the minority carrier lifetime of samples containing comparatively high dislocation density (10 4 –10 5 /cm 2 ) is shown to vary with the dislocation density, and the results is expressed in terms of two lifetimes: τ d , that associated with random dislocations, and τ b , that due to the recombination centers of an undetermined origin. It is also shown that anomalous temperature dependence of the steady-state photoconductivity of high-resistivity p -type nickel doped germanium can be interpreted by assuming that two acceptor levels of nickel atom ar...