Optical investigation of non-equilibrium carrier dynamics in differently doped VGF-grown ZnTe single crystals

摘要

We applied a time-resolved FWM technique to study the dynamics of photoexcited carriers in differently doped VGF-grown ZnTc crystals at room temperature. We observed a fast carrier trapping to deep levels in phosphorus doped and undoped samples. The measurements at below and above band-gap excitations revealed the much higher concentration of these levels near the surface than in the bulk in both samples. The concentration of deep traps has been estimated for phosphorus doped sample N-T =(1-2) x 10(15) cm(-3) in the bulk and N = (3-5) x 10(18) cm(-3) near the surface. In the undoped sample these traps are present at much higher concentration. The electron and hole mobilities mu(n) = (500 +/- 28) cm(2)/Vs and mu(h) = (16 +/- 6) cm(2)/Vs were estimated from the measured diffusion coefficient values D = (12.5 +/- 0.7) cm(2)/s in the p-type sample and D = (0.8 +/- 0.3) cm(2)/s in the semi-insulating one. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.