SURFACE STOICHIOMETRY VARIATION IN ALTERNATE MOLECULAR-BEAM EPITAXY OF GAAS

RHEED intensity has been used as a probe of the surface stoichiometry variation occurring in the molecular beam epitaxial (MBE) growth of GaAs when Ga and As are alternatively supplied to the surface. A comparison of the As surface coverage prior to the growth with the coverage reached at the end of each growth cycle gives evidence that As desorption during the Ga deposition sequence becomes significant above almost-equal-to 550-degrees-C. An extended As deposition time (with respect to the time required if no As desorption occurred) is then needed to recover, at the end of each growth cycle, the As surface coverage obtained in standard MBE growth using the same growth conditions (temperature and Ga and As4 flux intensities). However, even if the surface stoichiometry can be effectively recovered, a modification of the interface properties is observed through photoluminescence experiments on GaAs quantum wells (QWs) grown at 600-degrees-C by this modified MBE procedure.