X-ray diffraction study on GaAs(0 0 1)- 2 4 surfaces under molecular-beam epitaxy conditions

The GaAs(0 0 1)-(2 4) reconstructed surface was investigated by in situ surface X-ray diffraction. X-ray diffraction patterns were measured with increasing substrate temperature within the b phase of GaAs(0 0 1)-(2 4) in a constant As flux of 5 10 7 Torr. At relatively low temperatures up to 545 C, the observed X-ray diffraction patterns agree well with the b2(2 4) surface. However, a different X-ray diffraction pattern was obtained at temperatures close to the a phase, while the 2 4 periodicity still persisted. This change is explained by partial As-dimer desorption which results in a mixture of the b2(2 4) and a2(2 4) structures