Temperature effect of activation energy for GaSb quantum dots using variable temperature photoluminescence.

The excitation power dependence of radiative transitions in the type-II GaSb/GaAs quantum dots structure has been studied by the photoluminescence (PL) at different temperatures. The QDs' photoluminescence exhibits a strong blue-shift with increasing the excitation power and the peak energy (E(PL)) is proportional to the third root of excitation power. With the increase of excitation power, the nonlinear change for both the PL peak and the intensity was observed, which is attributed to the excited state transition. The thermal process and activation energy (E(a)) of electron-hole pairs at different excitation powers has also been studied for GaSb QDs. As the excitation power increases, the activation energy decreases, while E(PL) +E(a) keeps nearly constant, which is smaller than the band gap of GaAs. The decrease of E(a) is probably caused by the band bending effect.