Carrier dynamics in beta-Ga2O3 nanowires

Abstract

Carrier dynamics have been investigated in beta-Ga2O3 nanowires (NWs) grown by the vapor-liquid-solid mechanism, using ultrashort transient absorption spectroscopy in conjunction with time-correlating single photon counting photoluminescence. UV femtosecond pulse excitation has been utilized to generate nonequilibrium carrier distributions near the band edge of the NWs and nondegenerate pump-probe techniques have been employed to follow carrier relaxation through the defect related states located within the band gap of the NW semiconductor. Relaxation of the photogenerated carriers through these states appears to be biexponential with a fast component on the order of 3-5 ps and the slower component around 40-90 ps depending on the states being probed. Transient absorption intensity measurements reveal that recombination mechanisms such as Auger and bimolecular become contributing factors to the relaxation dynamics for absorbed fluences larger than 90 mu J/cm(2). In the low fluence regime, time-correlated single photon counting photoluminescence measurements revealed a nonradiative relaxation mechanism with time constants ranging from 0.6-1 ns and a radiative relaxation with a time constant of approximately 4 ns. (C) 2010 American Institute of Physics. [doi:10.1063/1.3520589]