Extremely long carrier lifetime over 200 ns in GaAs wall-inserted type II InAs quantum dots

Abstract

To realize highly efficient intermediate-band (IB) solar cells, long lifetime of photo-generated carriers in the IB is essential. For this purpose, we propose a concept for IB absorbers using GaAs wall-inserted type II InAs quantum-dots (QDs), in which electrons at the IB of the InAs QDs and holes in the valence band of the GaAsSb layers are farther separated compared to those in conventional type II QDs. We fabricated InAs/GaAs/GaAs0.82Sb0.18 type II QDs and performed time-resolved photoluminescence spectroscopy. The obtained lifetime was as long as 220 ns for electrons at the IB.