Annealing effects on the microstructure of Ge/Si(001) quantum dots

Ge/Si(001) multilayer islands produced by gas-source molecular-beam epitaxy at 575 degreesC were investigated using energy-filtering transmission elec tron microscopy. Results show, for as-grown samples, not only a continuous enlargement of island size in upper layers but also a continuous increase o f Ge concentration within islands in upper layers. As a result of the incre asing island size and Ge concentration within the islands, the island densi ty in upper layers decreases. For samples annealed at 900 degreesC for 5 mi n, the aspect ratio of buried islands increases significantly, and the aver age Ge concentration within islands of different layers becomes uniform. (C ) 2001 American Institute of Physics.