Temporal evolution of effects of ultrafast carrier dynamics in In_(0.33)Ga_(0.67)N: above and near the bandgap

摘要

Ultrafast carrier dynamics in the In_(0.33)Ga_(0.67)N epilayer were investigated in detail, using femtosecond transient differential non-degenerate optical absorption measurements. Following an excitation at 400 nm with fluence ranging from 25 μJ cm~(-2) to 3000 μJ cm~(-2), probing was carried out above and near the bandgap using different wavelengths generated from a super continuum source. We have found that bandgap renormalization plays a key role when probing at photon energies well above the bandgap and it is clearly distinct from other effects at the lowest fluence. The critical carrier density for the onset of noticeable bandgap renormalization effects in this material when probing well above the bandgap is approximately 5 x 10~(18) carriers cm~(-3). We have observed a decrease in the energy loss rate of this material as a function of photogenerated carrier density which is attributed to phonon bottleneck effect. For the lowest carrier density, we have extracted an optical phonon lifetime to be approximately 45 ± 9 fs.