Preparation of low dimensional structures by molecular beam epitaxy-regrowth on patterned AlGaAs buffer layers

Abstract

We studied the preparation of low dimensional structures by molecular beam epitaxy (MBE)-regrowth on patterned AlGaAs buffer layers. The detailed interface and surface structure was investigated by scanning electron microscopy and transmission electron microscopy. The active area on the patterned Al 0.33Ga 0.67As buffer layer was passivated by a thin GaAs cap layer which is thermally desorbed in the MBE system prior to overgrowth. Small {111}A and larger {311}A facets dominate the surface structure after MBE-regrowth on the etched ridges along the [0 1 ] direction within the (100) surface plane. Hall effect measurements demonstrate, that an electron concentration of 8 × 10 11 cm −2 is achieved in a 20 nm wide modulation doped quantum well with a regrown AlGaAs buffer layer thickness of only 65 nm. No free carriers are detected in the overgrown quantum well within the region where the etched Al 0.33Ga 0.67As surface was exposed to air.