Excitation-dependent carrier lifetime and diffusion length in bulk CdTe determined by time-resolved optical pump-probe techniques

We applied time-resolved pump-probe spectroscopy based on free carrier absorption and light diffraction on a transient grating for direct measurements of the carrier lifetime and diffusion coefficient D in high-resistivity single crystal CdTe (codoped with In and Er). The bulk carrier lifetime tau decreased from 670 +/- 50 ns to 60 +/- 10 ns with increase of excess carrier density N from 10(16) to 5 x 10(18) cm(-3) due to the excitation-dependent radiative recombination rate. In this N range, the carrier diffusion length dropped from 14 mu m to 6 mu m due to lifetime decrease. Modeling of in-depth (axial) and in-plane (lateral) carrier diffusion provided the value of surface recombination velocity S = 6 x 10(5) cm/s for the untreated surface. At even higher excitations, in the 10(19)-3 x 10(20) cm(-3) density range, D increase from 5 to 20 cm(2)/s due to carrier degeneracy was observed. Published by AIP Publishing.