Thermal emission in type-II GaSb/GaAs quantum dots and prospects for intermediate band solar energy conversion

Abstract

The electronic structure and thermal carrier capture and escape mechanisms are studied for GaSb/GaAs quantum dots with a type-II band alignment using admittance spectroscopy. Clear signatures are observed corresponding to confined quantum dot states with extracted activation energy of 0.337 eV and the thermal capture cross section in the range from 2.10 × 10−16 to 1.19 × 10−13 cm2. The thermal emission rates in the GaSb/GaAs quantum dots are significantly lower than prior reports for type-I systems, where optical emission is predicted to be the dominant process in an intermediate band solar cells under solar concentration.