Direct Measurement of Surface Defect Level Distribution Associated with GaAs Antiphase Boundaries

Using an electrostatic force microscope, we measure surface contact potential (SCP) variations across antiphase boundaries (APBs) on GaAs films grown on Ge substrates. The SCP at the APBs is consistently and reproducibly measured to be 30 mV higher than that at GaAs domains. This is due to Fermi levels being pinned at different surface states. The identical electrical behavior observed for all APBs indicates that they are the lowest energy (110) orientation. The sign of observed Fermi level shift is consistent with a prevalence of Ga-Ga bonds at real (110) APBs.