Direct measurement of surface defect level distribution associated with GaAs antiphase boundaries

Using an electrostatic force microscope, we measure surface contact potenti al (SCP) variations across antiphase boundaries (APBs) on GaAs films grown on Ge substrates. The SCP at the APBs is consistently and reproducibly meas ured to be 30 mV higher than that at GaAs domains. This is due to Fermi lev els being pinned at different surface states. The identical electrical beha vior observed for all APBs indicates that they are the lowest energy (110) orientation. The sign of observed Fermi level shift is consistent with a pr evalence of Ga-Ga bonds at real (110) APBs. [S0031-9007(98)08221-0].