STRUCTURAL AND OPTICAL-PROPERTIES OF VERTICALLY ALIGNED INP QUANTUM DOTS

Stacked layers of self-assembled InP quantum dots embedded in Ga0.52In 0.48P have been prepared by solid source molecular beam epitaxy. There by the distance between the dot layers has been varied from 2 to 16 nm , Cross sectional transmission electron microscopy shows that the InP dots are aligned in the growth direction [100]. As the distance betwee n the dot layers is reduced, each dot of the first dot layer is reprod uced in the upper layers, and this leads to an improvement of the dot size homogeneity of the stacked InP dot system. This is confirmed by p hotoluminescence (PL) measurements. which demonstrate a very narrow li newidth of 16 meV for a triple layer with 2 nm separation between the dot layers in comparison with a linewidth of 11 meV for a single layer sample. At the same time, the PL peak of the dots is shifted by 72 me V to lower energies which is ascribed to a reduced strain and strong e lectrical coupling between the densely stacked InP dots. (C) 1997 Amer ican Institute of Physics.