HIGH-RESOLUTION INSITU MEASUREMENT OF THE SURFACE-COMPOSITION OF INXGA1-XAS AND INXAL1-XAS AT GROWTH TEMPERATURE

The critical thickness for the onset of three-dimensional growth essentially depends, for InAs layers deposited by MBE on pseudomorphic layers on GaAs, on the indium composition of the surface monolayer prior to growth. This effect allows a direct and accurate in situ probing of the surface composition at growth temperature. The surface segregation of indium atoms could thus be quantitatively studied for InGaAs and InAlAs alloys. It is also possible to extract on the monolayer scale the actual composition profile of heterostructures, as demonstrated for a nominally one monolayer thick InAs quantum well in GaAs.