Optical properties and dynamics of excitons in Ga(Sb, Bi)/GaSb quantum wells: evidence for a regular alloy behavior

Optical properties and carrier dynamics in 6.6, 10.4, and 14.4 nm wide Ga(Sb, Bi)/GaSb quantum wells (QWs) with similar to 10%-11% of Bi were studied by photoluminescence (PL), time-resolved PL, and transient reflectivity. Experiments revealed that low temperature emission is strongly governed by the decay of excitonic population that undergoes weak localization on the QW potential fluctuations rather than the strong defect-like localization typically found for highly mismatched alloys. This statement is supported first by the nearly linear increase of the PL intensity with the excitation power, second, by the lack of the S-shape signature in the temperature-dependent PL studies, and third, the absence of a strong lifetime dispersion for excitons. The low-temperature intraband carrier relaxation time is established in the range of 14-19 ps, nearly independent on the well width, while the exciton lifetime exhibits a well width dependence, i.e. this time decreases from similar to 265 ps, through similar to 206 ps, to similar to 147 ps with the increase of the QW width from 6.6 to 14.4 nm. Our results demonstrate that in contrast to other dilute bismide alloys, GaSbBi behaves as a regular alloy rather than as a highly-mismatched material.