Spatially resolved deep level transient spectroscopy using a scanning tunneling microscope

A novel type of deep level transient spectroscopy (DLTS) capable of resolving the spatial distribution of deep levels in semiconducting crystals has been invented based on scanning tunneling microscopy (STM). The electrical contact in the conventional DLTS is replaced with the sharp tip in STM, which is not in contact with the sample surface. The transient signal detected in STM-DLTS is the surface photovoltage (SPV) induced by chopped illumination of the sample with a laser light. The decay rate of SPV on termination of illumination reflects the rate of detrapping of photo-generated carriers from deep centers located beneath the sample surface. The effectiveness of this method has been tested for a cleaved crystal of plastically deformed n-GaAs.