AC photoconductivity of type-II InAs/AlAs_1-xSb_x multi-quantum well structure

InAs/AlAs_1-xSb_x multi-quantum wells (MQW) are a promising way to understand solar cells design through engineering of long excited-state lifetime and inhibition of phonon interactions. A type-II MQW structure is investigated using time-resolved terahertz spectroscopy as a function of lattice temperature to determine the dynamics of hot carriers. For hot-carrier densities above the Mott density and at low-to-intermediate temperatures, metastability is observed during early times of the transient absorption signal, which exhibits a plateau in the excitation-photon-energy dependence. Meanwhile, AC photoconductivity spectra, analyzed using the Drude-Smith model, shows that the mobility of hot-carriers remains constant above the Mott density and increases with increased carrier recombination. Under the latter excitation conditions, the mobility is consistent with higher scattering rates, attributed to a contribution of L-valley scattering. Finally, the carrier mobility reduces with increasing lattice temperature, inhibited by a phonon bottleneck that keeping both hot carrier and phonon densities high. Therefore, understanding AC photoconductivity of type-II InAs/AlAsSb MQW structures will reveal potential pathways for the development of efficient hot-carrier-based solar cells.