Scanning Tunneling Microscopy and Barrier-Height Imaging of Subsurface Dopants on GaAs(110)

Abstract

Subsurface dopant atoms are investigated by scanning tunneling microscopy (STM) and barrier height (BH) imaging. The obtained BH image shows a local reduction in BH -(1–2) eV at positively charged donor sites while it shows a local increase in BH (1–5) eV at negatively charged surface Ga vacancies. Our results indicate that the charge-sensitive imaging can be accomplished by utilizing the STM–BH technique. A simple one-dimensional simulation of tunneling current through a STM junction on the GaAs(110) surface indicates that the results of BH imaging well reflect the charge state of the subsurface dopant or charged surface defects under appreciable electron accumulation conditions.