X-ray diffraction study on GaAs(0-bar 0-bar 1)- 2x4 surfaces under molecular-beam epitaxy conditions

The GaAs(0-bar 0-bar 1)-(2x4) reconstructed surface was investigated by in situ surface X-ray diffraction. X-ray diffraction patterns were measured with increasing substrate temperature within the β phase of GaAs(0-bar 0-bar 1)-(2x4) in a constant As flux of 5x10-7-bar Torr. At relatively low temperatures up to 545-bar -bar C, the observed X-ray diffraction patterns agree well with the β2(2x4) surface. However, a different X-ray diffraction pattern was obtained at temperatures close to the α phase, while the 2x4 periodicity still persisted. This change is explained by partial As-dimer desorption which results in a mixture of the β2(2x4) and α2(2x4) structures