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.