Size distribution and optical properties of self-assembled Ge on Si

The distribution of Ge islands is analysed in order to understand their opt ical behaviour. The Ce islands described in this paper were deposited by lo w-pressure chemical vapour deposition at relatively high temperature (700 d egrees C), therefore the diffusion length of adatoms is high (similar to 10 0 mu m) and thus, not the limiting factor for nucleation. By changing the d eposition time and the coverage, square-based pyramids, domes and relaxed d omes are nucleated. Mainly domes emit light, the emission being in the wave length range 1.38-1.55 mu m. When pyramids or relaxed domes are present, th e photoluminescence broadens and decreases in intensity. The electrolumines cence of vertically correlated islands increases with the number of layers, i.e. with the number of islands. The nucleation of islands on patterned (0 01) Si is changed when the deposition is performed on Si mesas with high in dex facets. The size distribution becomes narrower when the mesa size is de creased. An intermixing of up Bo 40% Si in the 2D layer was determined from photoluminescence data. PIN diodes fabricated on patterned wafers show an area-dependent electroluminecence related to a different microstructure of islands on large and small mesas. Finally, the lateral ordering on {hkl} fa cets is discussed.