Minority-carrier diffusion-length measurement and lifetime in Pb0.8Sn0.2Te and indium-doped PbTe liquid phase epitaxy layers

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Minority carrier diffusion length was measured between 10–110 K, using a laser light spot scanning technique in Pb0.8Sn0.2Te and In-doped PbTe layers, grown by liquid phase epitaxy. A new method for fabricating diodes with a beveled surface is described. Diffusion lengths L of about 10 and 1 μm were measured in Pb0.8Sn0.2Te epilayers grown at 500 and 600 °C, respectively. In indium-doped PbTe epilayers, L varies with temperature in the range 0.2 to 1.6 μm. The measured diffusion length was used with available mobility data to derive the minority-carrier lifetime in these epilayers. Comparison of the experimental results with theory shows that in undoped Pb0.8Sn0.2Te, carrier lifetime is dominated by band-to-band radiative and Auger recombination mechanisms, while in In-doped PbTe, recombination takes place via nonradiative centers. The implications of the observed diffusion length and the derived lifetime values on the performance of optoelectronic devices are discussed.