MORPHOLOGICAL TRANSITION OF INAS ISLANDS ON GAAS(001) UPON DEPOSITION OF A GAAS CAPPING LAYER

The interaction between a GaAs cap and InAs islands grown on vicinal GaAs(001) has been studied by transmission electron microscopy and atomic force microscopy. Samples were prepared by molecular beam epitaxy at 480 degrees C. Upon GaAs cap deposition, it was found that the previously grown InAs islands undergo a novel type of morphological transition, i.e., a transition from disk-shaped to ring-shaped islands. InAs becomes depleted or entirely absent in the central area of what had been a disk-shaped InAs island. The GaAs cap was also shown to be virtually absent within the same central region, resulting in the formation of crater-like surface depressions.