Suppression of phonon-mediated hot carrier relaxation in type-II InAs/AlAsxSb1 − x quantum wells: a practical route to hot carrier solar cells

InAs/AlAsxSb1 − x quantum wells are investigated for their potential as hot carrier solar cells. Continuous wave power and temperature‐dependent photoluminescence indicate a transition in the dominant hot carrier relaxation process from conventional phonon‐mediated carrier relaxation below 90 K to a regime where inhibited radiative recombination dominates the hot carrier relaxation at elevated temperatures. At temperatures below 90 K, photoluminescence measurements are consistent with type‐I quantum wells that exhibit hole localization associated with alloy/interface fluctuations. At elevated temperatures, hole delocalization reveals the true type‐II band alignment, where it is observed that inhibited radiative recombination due to the spatial separation of the charge carriers dominates hot carrier relaxation. This decoupling of phonon‐mediated relaxation results in robust hot carriers at higher temperatures, even at lower excitation powers. These results indicate type‐II quantum wells offer potential as practical hot carrier systems. Copyright © 2016 John Wiley & Sons, Ltd. Type‐II InAs/AlAs1‐xSbx QWs are investigated as a candidate system for hot carrier solar cells. Between 10K and 90K the increased contribution of phonon‐mediated relaxation pathways reduces the non‐equilibrium carrier temperature. However, above 90K an unconventional increase in the hot carrier temperature becomes evident despite increasing phonon densities. This behavior is attributed to the spatial redistribution of holes and subsequent increase in lifetime of the electrons, which produces a bottleneck that effectively decouples phonon relaxation at higher temperature.