Investigation of hot carrier relaxation in type II systems via ensemble Monte Carlo simulation

Type-II InAs/AlAsSb multi-quantum well (MQW) structures have seen usage in both quantum-cascade lasers and avalanche photodiodes. There has been recent interest in investigating this material system for next-generation photovoltaic applications, specifically hot carrier solar cells, due to the type-II offset spatially separating electrons and holes and the predicted high LO phonon lifetime. In order to successfully realize a hot carrier solar cell, the ultrafast relaxation process needs to be well understood. To investigate these effects, we simulated a MQW structure under both pulsed and continuous wave laser excitation with an Ensemble Monte Carlo (EMC) solver self-consistently coupled to a multi-valley non-parabolic Schrödinger/Poisson solver. The EMC includes intervalley scattering, carrier-carrier scattering, and nonequilibrium phonon effects.The EMC simulations show that the inhibited cooling is primarily due to a build up of LO phonons. We demonstrate good agreement with temperatures extracted via photoluminesce techniques.