Characterization of InAs dots on n-GaAs by AFM with a conductive tip

Abstract

We performed atomic force microscopy (AFM) on an InAs-covered GaAs surface on which InAs dot structures are formed surrounded by a wetting layer. In order to characterize its surface band structures, we applied an a.c. bias voltage ( f =25 kHz) between a conductive AFM tip and a sample. By means of a lock-in detection technique, clear electrostatic force images as well as topographic images were obtained with high resolution. The electrostatic force images of the different frequency components ( f and 2f ) reveal that the gap width between the tip and the conductive region of the sample is modulated very little by the bias voltage in the dot-covered area, whereas the gap width is obviously modulated in the wetting layer area. These results indicate that the surface depletion is more suppressed in the dot-covered area than in the wetting layer area. Copyright © 1999 John Wiley & Sons, Ltd.