FOURIER TRANSIENT GRATING IN SEMICONDUCTORS WITH NONLINEAR CARRIER RECOMBINATION

Sinusoidaly excited free-carrier transient gratings (TG) are widely us ed for investigation of transport properties in bulk or in thin film s emiconductors. The sinusoidal TG shape of the carrier dynamics persist s only for linear recombination and does not occur in the case of stri ctly nonlinear carrier recombination. In this paper we present an accu rate procedure for a numerical Fourier TG analysis in the case of an a rbitrarily shaped transient grating. Time-resolved simulations are dem onstrated for a semiconductor in the presence of Auger-type carrier re combination. We show that two excitation regimes, namely the low-modul ation sinusoidal profile and the high-modulation rectangular profile w ilt enable us to separate the Auger recombination rate from the carrie r diffusivity as a function of injected carrier concentration by using the fundamental and/or the higher-frequency spatial modes. Our analys is points out that correct prefactor of the Auger recombination terms has to be used in the evaluation of differently shaped TGs.