Comparative Study of Ultrafast Intersubband Electron Scattering Times at ~1.55 mum Wavelength in GaN/AlGaN Heterostructures

We report on a comparative study of room temperature intersubband electron scattering lifetimes in GaN/AlGaN single and coupled double multiple quantum well samples with peak absorption wavelengths ranging from 1.4 to 1.7 mum. Using time-resolved pump-probe spectroscopy, electron scattering times as short as ~160 fs have been measured for a coupled QW sample and ~300 fs for single QW samples. While no significant dependence on the excitation power has been observed, a decrease of the scattering times with increasing probe wavelength has been measured and may be attributed to monolayer fluctuations in the samples.