Type-I optical emissions in Ge/Si quantum dots

The authors studied the optical emission of Ge∕Si quantum dots under externally applied biaxial stress using samples grown with different temperatures varying from 430to700°C. The optical emission energy of samples grown at low temperatures is rather insensitive to the applied external stress, consistent with the type-II band alignment. However, for samples grown at high temperatures we observed a large blueshift, which suggests type-I alignment. The result implies that recombination strength can be controlled by the growth temperature, which can be useful for optical device applications.