Investigation of InAs/GaAs Quantum Dots with a Ballistic Electron Emission Microscope

Austin R. Carter

A scanning tunneling microscope (STM) was converted to a ballistic electron emission microscope (BEEM). STM/BEEM images were taken of a variety of conductive and non-conductive samples including an InAs/GaAs quantum dot BEEM sample. For small scans with high scan rates, changes in the BEEM images directly correlate to sample features such as topography and subsurface electronic properties. It was qualitatively determined that the degree to which these BEEM images correlate to a feature depends on the tip bias. Small tip biases less than 1000 mV produce relatively flat BEEM images while large tip biases produce BEEM images heavily correlated to sample features. Improvements to the amplification of the BEEM current as well as suggestions for future ballistic electron emission spectroscopy measurements are described.