Free-exciton luminescence in GaSb quantum wells confined by short-period AlSb-GaSb superlattices

Abstract

Photoluminescence and photoluminescence excitation measurements at temperatures ranging from 4 to 300 K were performed on 9.2-nm GaSb quantum wells confined by AlSb-GaSb short-period superlattices. In the temperature range 4–200 K the photoluminescence from the high-quality molecular beam epitaxially grown samples is dominated by free-exciton emission. This assignment is confirmed by photoluminescence excitation spectroscopy which reveals an energy separation of 11.5 meV between n=1 heavy-hole and n=1 light-hole free excitons for the 9.2-nm wells. At low temperatures the photoluminescence line is shifted by only 7.5 meV to low energy from the heavy-hole excitonic peak observed in the excitation spectrum. This small value of the Stokes shift indicates the absence of impurity-related trapping of excitons.