SURFACE CORRUGATION OF GAAS-LAYERS GROWN ON (775)B-ORIENTED GAAS SUBSTRATES BY MOLECULAR-BEAM EPITAXY

Surface morphologies of GaAs layers grown on (775)B-oriented GaAs subs trates by molecular beam epitaxy were studied using atomic force micro scopy. The surface of a GaAs layer grown on a (775)B GaAs substrate is flat when it is grown at a substrate temperature (T-s) below 580 degr ees C, but corrugates regularly for T-s' greater than or equal to 640 degrees C. Similar periodic corrugation of the (775)B GaAs surface for med during thermal annealing at T-s = 640 degrees C under As-4 atmosph ere (10(-6) Torr), which is similar in shape to that of a GaAs layer i n the early stage of growth (a GaAs layer thinner than 5 nm). As the t hickness of a GaAs layer increases from 5 nm, the lateral period and s tep height of the corrugation increase and tend to saturate for thick GaAs layers (200 nm thick or more). The precise structure of the surfa ce corrugation of a 3-nm-thick GaAs layer (the lateral period of 12 nm and step height of 1.2 nm) was observed as a corrugated AlAs-on-GaAs interface of a GaAs/(GaAs)(5)(AlAs)(5) quantum well structure with an average well width of 3 nm by cross-sectional transmission electron mi croscopy observation.