MONOLAYER SCALE STUDY OF SEGREGATION EFFECTS IN INAS GAAS HETEROSTRUCTURES/

We grow by molecular beam epitaxy and study by low temperature photolu minescence and high resolution electron microscopy pairs of identical AlAs/GaAs quantum wells, in which an InAs monolayer is inserted at nom inally symmetric positions in the well, close to one or the other inte rface. The absolute displacement of indium atoms due to surface segreg ation processes is studied with respect to the well-defined GaAs/AlAs interfaces. Both techniques show that the InAs-on-GaAs interface lies at its nominal position, which gives the first clear example of a kine tical freezing of segregation processes in semiconductor heterostructu res. PL data allow us to refine previous estimates of the segregation efficiency and to compare quantitatively various growth techniques.