PREPARATION OF LOW-DIMENSIONAL STRUCTURES BY MOLECULAR-BEAM EPITAXY-REGROWTH ON PATTERNED ALGAAS BUFFER LAYERS

We studied the preparation of low dimensional structures by molecular beam epitaxy (MBE)-regrowth on patterned AlGaAs buffer layers. The det ailed interface and surface structure was investigated by scanning ele ctron microscopy and transmission electron microscopy. The active area on the patterned Al0.33Ga0.67As buffer layer was passivated by a thin GaAs cap layer which is thermally desorbed int he MBE system prior to overgrowth. Small {111}A and larger {311}A facets dominate the surfac e structure after MBE-regrowth on the etched ridges along the [01BAR1] direction within the (100) surface plane. Hall effect measurements de monstrate, that an electron concentration of 8 x 10(11) cm(-2) is achi eved in a 20 nm wide modulation doped quantum well with a regrowth AlG aAs buffer layer thickness of only 65 nm. No free carrier are detected in the overgrown quantum well within the region where the etched Al0. 33Ga0.67As surface was exposed to air.