Temperature dependence of photoluminescence from self-organized Ge quantum dots with large size and low density

Photoluminescence (PL) from self-organized Ge quantum dots (QDs) with large size and low density has been investigated over a temperature range from 10 to 300 K using continuous-wave (CW) optical excitation. The integrated PL intensity of QDs observed is negligible at about 10 K and rapidly increases with raising temperature up to 100 K. Through analyzing the PL experimental data of the QDs and wetting layer (WL), we provide direct evidence that there exists a potential barrier, arising from the greater compressive strain surrounding large QDs, which could trap carriers in WL at low temperatures and could be overcome via increasing temperature.