INFLUENCE OF VARIOUS GROWTH-PARAMETERS ON THE INTERFACE ABRUPTNESS OFALAS GAAS SHORT-PERIOD SUPERLATTICES/

Cross-sectional scanning tunneling microscopy has been used to investi gate the effects of several key growth parameters on the resulting int erfacial quality of AlAs/GaAs short period superlattices. For growth o n top of AlGaAs layers, only superlattices grown with periodicity no s maller than 4 unit cells of GaAs and 2 unit cells of AlAs and grown wi th a minimum of 30 s of growth interrupt time are resolved. On the oth er hand, when grown on top of GaAs layers, superlattices as fine as 2 unit cells of GaAs and 1 unit cell of AlAs grown with only 5 s of-grow th interrupt time are resolved. This result suggests that the material on which the superlattice is grown is at least as important as the gr owth interrupt time. Tn particular, GaAs seems to provide a smoother s tarting surface than AlGaAs and hence aids in the formation of abrupt interfaces. We also compare our scanning tunneling microscopy data wit h some predictions based on simple atomic models of the interfacial re gions. (C) 1995 American Vacuum Society.