Groups of Ge nanoislands grown outside pits on pit-patterned Si substrates

Abstract

Ordered arrays of Ge quantum dot groups (QDs) were grown on pit-patterned silicon-on-insulator (SOI) substrates with deep pits, prepared by electron beam lithography (EBL) and plasma-chemical etching (PCE). Experiments were carried out for the square and hexagonal pit lattices with the lattice period varied. The QDs were found to be sited at the periphery of pits. It was demonstrated that for both pit lattice types the number of QDs per pit can be controlled by varying the period of the pit lattice. The Monte Carlo (MC) simulations of QDs growth on pit-patterned Si substrates were carried out, using the model, which takes strain into account. The island patterning depending on the inter-pit distance is interpreted as the result of competition between stress-driven QD nucleation and Ge migration downward into the pits, which serve as the sinks for Ge atoms.