Electron lifetime and diffusion constant in germanium-doped gallium arsenide

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Abstract
The lifetime of electrons in Ge-doped p-type GaAs grown by liquid phase epitaxy has been determined as a function of doping level using an optical phase-shift technique. The internal radiative efficiency of this material is found to be high even at room temperature. Furthermore, the electron lifetime τ has been measured in Ge-doped samples compensated with Sn donors. Data are presented both for 300°K and 77°K. Measurements of the diffusion length on the same samples are also presented. From the combined results the diffusion constant of the electrons is obtained as a function of doping level both for the Ge-doped and the Ge-doped Sn-compensated samples. In GaAs doped with Ge only, τ at 300°K is inversely proportional to the hole concentration p; at this temperature partial compensation with Sn donors has only an effect at higher hole concentrations. At 77°K, the τ values depend more strongly on the degree of compensation. Conclusions regarding the influence of band tailing are presented.