OPTICAL-PROPERTIES OF VERTICALLY STACKED INAS ISLAND LAYERS GROWN ON (311)A B AND (001)GAAS SUBSTRATES/

The optical properties of vertically stacked InAs island layers grown by molecular beam epitaxy on (311)A/B and (001) GaAs substrates have b een studied by means of photoluminescence (PL) and transmission electr on microscopy (TEM) measurements. These properties were systematically investigated as a function of spacer layer thickness, orientation, an d temperature. Spacer layer thickness variation exhibits influence on PL spectra for all orientations. Differences in peak shape, position, amplitude and integrated photoluminescence have also been observed for all surfaces. The results show an increase of integrated PL intensity of similar to 5 times and a decrease of spectral linewidth compared w ith a single set of islands, suggesting a possible electronic coupling between the layers. In addition, in the case of (311)A, the structure does not exhibit QD formation. (C) 1998 Elsevier Science B.V. All rig hts reserved.