Imaging and Spectroscopy of Single InAs Self-Assembled Quantum Dots using Ballistic Electron Emission Microscopy

Single InAs self-assembled quantum dots buried spatially beneath a Au/GaAs interface are probed for the first time using the imaging and spectroscopic modes of ballistic electron emission microscopy (BEEM). BEEM images show enhanced current through each dot. Spectra taken with the tip positioned on a dot show shifted current thresholds when compared with the off dot spectra, which are essentially the same as those of Au on bulk GaAs. Shifts in the $\gamma$ and $L$ conduction band thresholds are attributed to strain in the GaAs cap layer. Fine structure below the $\gamma$ threshold is consistent with resonant tunneling through zero-dimensional states within the quantum dots.