Transient drift velocity of photoexcited electrons in CdTe

The relaxation dynamics of photoexcited carriers of CdTe is vital toward its applications in high-performance optoelectrical devices. In this paper, the dependences of transient drift velocities of photoexcited electrons in bulk CdTe on photoexcitation conditions such as the pump intensity and photoexcitation wavelengths, temperature and externally applied electric field, are systematically investigated by the ensemble Monte Carlo method (EMC). The main scattering mechanisms including nonelastic deformation potential acoustic phonon, deformation potential optical phonon scattering, ionized impurity (II) scattering, and polar optical phonon scattering events, the effects of nonequilibrium phonons, and the Pauli exclusion principle are considered in EMC. The velocity overshoot phenomenon is only found to arise at a low temperature (100 K), with a longer photoexcitation wavelength (640 nm) and under a higher electric field (> 50 kV/cm). The effect of nonequilibrium phonons on electron drift velocity is found to be dependent on the photoexcited carrier density. Our findings may be useful for designing novel CdTe-based optoelectronic devices, which employ nonequilibrium photoexcited carriers to improve the performance.