Comparative study of ultrafast intersubband electron scattering times at ∼1.55 μm 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 (QW) samples with peak absorption wavelengths ranging from 1.4 to 1.7 μm. Using time-resolved pump-probe spectroscopy electron scattering times as short as $\text{∼160\hspace{0.17em}}\mathrm{fs}$ have been measured for a coupled QW sample and $\text{≲300\hspace{0.17em}}\mathrm{fs}$ 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.