Peculiarities of the MBE growth of nanowhiskers on GaAs(100) substrates

Abstract

We have studied the formation of nanowhiskers (NWs) by molecular beam epitaxy (MBE) on GaAs(100) substrates. The MBE growth of NWs exhibits two stages (initial and developed) and leads to the formation of NWs with surface morphology of two types (nucleation and intergrowth). The stage of developed growth is characterized by the predominant formation of intergrown NWs oriented in the 〈111〉B direction, having (110) habit (including the NW tip surface) and hexagonal cross sections with a transverse size within 50–300 nm. It was found that the transverse size of a hexagonal NW may significantly differ from that of an Au-GaAs melt droplet. The ratio of longitudinal and transverse dimensions of intergrown NWs can be on the order of 150 and above. When the transverse size of NWs exceeds a certain value (about 200 nm), the crystal length exhibits a slight decrease. The existence of two types of morphology is indicative of inhomogeneous character of the NW growth on a GaAs(100) surface, which depends on the catalyst droplet size, effective thickness of the deposited GaAs layer, and the growth temperature.