Ordered quantum dot formation on GaSb surfaces during ion sputtering

Abstract

We have recently reported an alternative technique for the generation of ordered nanometer quantum dots on III–V semiconductor surfaces via self-organized patterning by ion sputtering [S. Facsko et al., Science 285 (1999) 1551]. Ripple formation induced by ion sputtering has been observed in a wide variety of materials under non-normal incidence. In contrast to this, normal incidence ion bombardment leads to the formation of uniform dots on GaSb surfaces ordered in a hexagonal array. The dots have a highly crystalline structure and an aspect ratio of 1. Due to the low energy of the ions, only the topmost 2 nm are damaged by the ion beam. The formation process of nanoscale dots is based on an instability that arises from the curvature dependence of the sputter yield. The interplay between this instability and surface smoothing mechanisms creates a surface morphology dominated by a single wavelength. Sputtering the stable surface structures down to an interface with a larger bandgap material below produces isolated quantum dots that show electrical confinement. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies are performed here to characterize the fabricated quantum dot structures.