Material properties of Pb1-xSnxSe epilayers on Si and their correlation with the performance of infrared photodiodes

Hall mobilities and resistance area products R(o)A of infrared diodes in epitaxial Pb1-xSnxSe layers on CaF2 covered Si(111) substrates were correlated with threading dislocation densities rho. The low temperature saturation Hall mobilities were entirely determined by rho and proportional to their mean spacing 1/root rho. For the photodiodes, the R(o)A values at low temperatures were inversely proportional to rho. A model where each dislocation in the active area of the diodes causes a shunt resistance correctly describes the results, the value of this resistance for a single dislocation is 1.2 G Omega for PbSe at 85K. The dislocation densities were in the 2 x 10(7) to 5 x 10(8) cm(-2) range for the 3-4 mu m thick as-grown layers. Higher R(o)A values are obtainable by lowering these densities by thermal annealing, which sweeps the threading ends of the misfit dislocations to the edges of the sample.