SURFACE STOICHIOMETRY VARIATION ASSOCIATED WITH GAAS (001) RECONSTRUCTION TRANSITIONS

GaAs (001) surface structural transitions induced by Ga deposition have been studied through the correlation between RHEED specular beam intensity variations and observed reconstruction changes. Surface stoichiometry variations associated with the onset of each surface reconstruction have been measured. From the best defined 2 x 4 reconstruction to the onset of the 3 x 1 and 4 x 6 reconstructions. As surface coverage variations of 0.31 and 0.53 ML are found, respectively. Results are also obtained for other surface reconstructions: c(4 x 4), 4 x 8 (reported for the first time in MBE) and 4 x 2. In addition, our study clearly shows that each surface reconstruction exists over a rather wide surface stoichiometry range.