Large-Signal Photoconductive Effect

Abstract

The theory of the photoconductive effect in semiconductors is extended to include nonlinear recombination rates. A method for determining the excess majority‐carrier density and lifetime (defined by the non‐linear recombination rate) as functions of the excess minority‐carrier concentration is developed from this theory and applied to experimental measurements on a p‐type sample of InSb at 80°K. After an initial sharp decrease from its small signal value of 5.2×10⁻⁶ sec the hole lifetime becomes constant at a value ∼3.05×10⁻⁶ sec when the excess electron concentration increases from 6.0×10⁹ cm⁻³ to the maximum value investigated, 15.5×10⁹ cm⁻³. The monotonic increase of the excess hole concentration Δp with excess electron concentration shows a tendency to flatten off at the higher densities (Δp=6.2×10¹³ cm⁻³ when Δn=15.5×10⁹ cm⁻³). A previous theory for the large‐signal photomagnetoelectric effect by the present authors is modified by the removal of the assumption that the excess majority‐carrier concentration be much smaller than the corresponding thermal equilibrium concentration. The resulting corrections (∼15%) to the graphs of electron lifetime and electron surface recombination velocity as functions of excess electron density, for the same sample of p‐type InSb that was used in the present investigation, are also presented.