Local optical characterization related to Si cluster concentration in GaAs using scanning tunneling microscope cathodoluminescence spectroscopy

We studied local optical properties of Si-doped GaAs(110) surface by scanning tunneling microscope cathodoluminescence (STM-CL) spectroscopy. where low-energy (similar to 100 eV) electrons field-emitted from STM tips were used as bright excitation sources. Each STM-CL spectrum of the GaAs surface showed a sharp GaAs band-edge emission peak and a broad peak at similar to 1 eV related to Si clusters composed of Si impurities and vacancies. The intensity ratio of the sharp peak to the broad peak in the STM-CL spectrum depended on the measurement position under the same excitation density. This locality is considered to be originated from the local Si cluster concentration. We also observed the correlation between the redshifts of the band-edge emission peaks and high Si impurity concentrations. Our study demonstrated that STM-CL spectroscopy is a useful tool to evaluate the local Si Cluster concentration with high spatial resolution.