RHEED STUDIES OF GA DESORPTION FROM GAAS AND OF AS DESORPTION FROM SI-DOPED GAAS DURING GROWTH INTERRUPTION

We obtain accurate measurements of Ga desorption rate under conditions of Knudsen evaporation between 600 and 630-degrees-C from (001) GaAs or AlAs using only RHEED. Within two monolayers from an AlAs interface the Ga desorption is reduced by a factor of 2.5-3. In another experiment we observe that a partial surface coverage of a GaAs surface by Si has no effect on Ga desorption but increases strongly the As desorption, leading accordingly to a lowering of the transition temperature to a Ga-rich surface.