Concentration dependence of the minority carrier diffusion length and lifetime in GaP

The minority carrier diffusion length and lifetime have been determined in Zn-doped p-type and in undoped and S-doped n-type GaP grown by liquid phase epitaxy, from the spectral response of Schottky diodes, and the decay of cathodoluminescence respectively. Below 10 18 cm −3 the quantities are independent of donor or acceptor concentration, and typical values are 6 μm and 120 ns in n-type, and 3 μm and 30 ns in p-type material. At higher concentrations the values fall rapidly. Electron injection efficiencies in p-n junctions are calculated from the data and are in agreement with diode efficiency measurements. The electron injection efficiency is shown to be a maximum at a donor concentration of 1 × 10 18 cm −3 for a typical lamp structure. Diffusion length can also be derived from the variation of photocurrent with diode capacitance, but low values are obtained. The divergence is explained in terms of recombination in the space-charge layer.