Determination of carrier diffusion coefficient and lifetime in single crystalline CVD diamonds by light-induced transient grating technique

Abstract

We report on a contactless, all-optical study of carrier diffusion and recombination kinetics in single-crystalline diamond layers using the light-induced transient grating (LITG) technique. Decay times of transient diffraction grating yielded carrier lifetime of tau(R) approximate to 3 ns and bipolar diffusion coefficient D-a = 12 cm(2)/s at 300 K. The latter value of D-a was found to be 4-5 times lower than the ambipolar diffusivity based on electron and hole mobilities, measured by photo-electrical time-of-flight (ToF) technique. This discrepancy was attributed to the bandgap renormalization at high excess carrier densities and its impact on carrier diffusion. The significant decrease of low temperature diffusivity pointed out to a contribution of many-body effects which are tentatively attributed to the formation of electron-hole liquid (EHL) at T < 150 K. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim