Scanning near-field cathodoluminescence microscopy for semiconductor investigations: A theoretical study

Abstract

The spatial resolution and the near-field signal detection efficiency obtained in scanning near-field cathodoluminescence microscopy (SNCLM) are theoretically evaluated in the case of semiconductor investigation. The effect of the electron-beam interaction volume, the surface recombination velocity, and the energy diffusion is taken into account. The lateral resolution of the SNCLM, because of the near-field collection mode, is not energy-transfer dependent. A good lateral resolution can be obtained even when the surface recombination velocity is low and the minority-carrier diffusion length is large [this is the advantage of the near-field collection mode with respect to the tip illumination/far-field collection mode generally used in photoluminescence (PL) imaging]. Further, it is shown that the radiative recombination centers situated far from the tip can perturb the near-field detection efficiency, particularly for large nonradiative surface recombination velocities and low diffusion lengths. Nevertheless, the short range of the electron energy loss limits the contribution of these luminescent centers. Consequently, the near-field/far-field contribution ratio in cathodoluminescence experiments is better than that of PL experiments done in the far-field illumination/tip collection mode for which the far-field signal is more important because of the large laser-beam excitation area.