Influence of ex-situ AFM treatment on epitaxial growth of self-organized InAs quantum dots

摘要

Self-assembled InAs quantum dots (QDs) have been the subject of intense research in part due to their potential for quantum information systems. However, many quantum information schemes require placing quantum dots at predetermined positions. Local anodic oxidation (LAO) on the base of atomic force microscope (AFM) is considered to be an effective tool for ex-situ patterning of GaAs substrate for further site-controlled growth of InAs quantum dots. We have experimentally shown that ex-situ AFM scanning without LAO (both in tapping and contact mode) of epitaxial GaAs surface modifies locally its properties while the surface topology remains unchanged. It has been revealed that AFM-treated area shows nucleating processes in MOCVD growth completely different from that of untreated area. The processes are found to be critical for growing of self-organized InAs quantum dots. Local surface density of grown quantum dots is significantly reduced in the AFM-treated area and its value depends on the number of the scan cycles. In the same epitaxial process the local surface density of quantum dots may be varied from 10~(11) cm~(-2) to 10~(7)cm~(-2). We discuss the nature of the observed phenomena in particular AFM-induced changes in surface potential. The observed effect in combination with LAO may be considered as a new tool for engineering surface density and position of epitaxially grown quantum dots.