Index of content:
Volume 85, Issue 5, 01 March 1999
- GENERAL PHYSICS: NUCLEAR, ATOMIC, AND MOLECULAR (PACS 01-39)
85(1999); http://dx.doi.org/10.1063/1.369622View Description Hide Description
We apply electrostatic force microscopy (EFM) to study defects in GaAs films grown on Ge. On a GaAs film with surface antiphase boundaries (APBs), we reproducibly measure the surface contact potential (SCP) at the APBs to be (30±5) mV higher than that of the domains, due to the surfaceFermi level at APBs being pinned closer to the valence band maximum. On a thick film which contains buried APBs and wedge-shaped depressions on the surface, we find that the SCP of the wedge-shaped depressions is (25±5) mV lower than that of the GaAssurface. Hence, these wedge-shaped depressions have defect electronic states different from those of APBs. The capacitance gradient contrasts on the two samples are also shown to arise from different origins. Factors that can affect the measured SCP and values are discussed. We demonstrate a new application of EFM to distinguish different types of defects by measuring variations in relative SCP (thus the work function or position of Fermi level) and/or on sample surfaces. The spatial resolutions of SCP and are 30 nm, limited by the tip size.