DOMAIN FORMATION ON THE RECONSTRUCTED GAAS(001) SURFACE

We have investigated the transition of the GaAs(001) surface from the As rich to the Ga rich phases in the reconstruction phase diagram by in-situ scanning tunneling microscopy (STM) and reflection high energy electron diffraction (RHEED). The initial surface prepared by molecular beam epitaxy (MBE) and monitored by RHEED shows a regular (2 x 4) As stabilized reconstruction. The different stages of the transition are achieved by post-growth annealing under ultrahigh vacuum conditions. STM images illustrate the flexibility of the GaAs(001) surface to adapt itself to changes on the growth conditions by forming various reconstructions and domain structures. Especially near the transition from the As to the Ga terminated surface, As rich (2 x 6) and Ga rich (4 x 2) domains exist at the same time. A domain structure formed in this way leads to the well known (4 x 6) RHEED pattern which is thus nor an intrinsic reconstruction. At even higher annealing temperatures large scale STM images reveal characteristically shaped step bunches and multilayer high steps due to sublimation of GaAs.