Phonon linewidths in InAs/AlSb superlattices derived from first-principles - Application towards quantum well hot carrier solar cells

Hot electrons generated by the absorption of high-energy photons typically thermalize by dissipating energy through phonon mediated relaxation pathways. Existence of non-equilibrium optical phonon populations (hot phonons) can suppress thermalization of electrons by facilitating a stable hot carrier population. In this work, we derive optical phonon scattering rates in InAs/AlSb superlattices using first-principles calculations and compare them with bulk InAs. Computations are performed for the two shortest period superlattices with equal widths of InAs and AlSb. While in pure InAs, the highest optical phonon scattering rates reach 5 cm^-1; in the superlattice, the peak scattering rates of optical phonons with frequencies above the energy gap, are much smaller, reaching ∼1 cm^-1. These lower scattering rates in the superlattice have important implications for design of high efficiency hot carrier solar cells and explain some of the robust hot carriers observed recently in InAs/AlAsSb quantum wells.