Height control of InAs/GaAs quantum dots by combining layer-by-layer in situ etching and molecular beam epitaxy

Abstract

A technique for controlling the height of InAs quantum dots (QDs) on GaAs surfaces is proposed and investigated. This technique involves combining layer-by-layer in-situ AsBr3 etching and molecular beam epitaxy (MBE). One layer of InAs QDs in Stranski–Krastanow (SK) growth mode is initially deposited on a GaAs surface by MBE. After growth of a thin GaAs layer on the InAs SK QDs, in situ etching of this thin GaAs layer creates an array of nanoholes vertically aligned with the underlying SK QDs on the etched GaAs. The nanoholes offer highly selective nucleation centers for the subsequent growth of InAs QDs. Finally, a second-layer of QDs is grown by providing InAs in limited quantity of about 1 monolayer (ML). Atomic force microscopy surface observations show that the nanoholes are completely filled, and that a planar growth surface is obtained with ∼1 ML. Furthermore, cross-sectional structural observations with a transmission electron microscope and energy dispersive x-ray analysis reveal that vertically overlapping InAs QDs are achieved. These results demonstrate that this technique can be applied to form height-controlled InAs QDs.