Comparison between Electron Beam and Near-Field Light on the Luminescence Excitation of GaAs/AlGaAs Semiconductor Quantum Dots

To precisely estimate electron beam excitation intensity and to understand exactly the electron beam excitation process in a semiconductor, we observed and compared the luminescence properties of GaAs/Al_0.3Ga_0.7As self-assembled quantum dots (QDs) by the cathodoluminescence (CL) and near-field scanning optical microscopy (NSOM) techniques. The actual excitation densities measured by the CL and NSOM techniques are nearly equal at the dose rates considered, except for a low dose rate in which the actual excitation density measured by the CL technique is slightly larger than that measured by NSOM technique. However, the difference between these excitation densities is extremely small relative to the expected value when electron-hole (e-h) pairs are temporarily densified as a result of a cascade process. Therefore, the spatially inhomogeneous distribution of e-h pairs in the generation and diffusion regions is considered to be the main cause of the small difference in excitation density in such a case.