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

The spatial resolution and the near-field signal detection efficiency obtai ned in scanning near-field cathodoluminescence microscopy (SNCLM) are theor etically evaluated in the case of semiconductor investigation. The effect o f 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-transfe r dependent. A good lateral resolution can be obtained even when the surfac e recombination velocity is low and the minority-carrier diffusion length i s large [this is the advantage of the near-field collection mode with respe ct to the tip illumination/far-field collection mode generally used in phot oluminescence (PL) imaging]. Further, it is shown that the radiative recomb ination centers situated far from the tip can perturb the near-field detect ion efficiency, particularly for large nonradiative surface recombination v elocities and low diffusion lengths. Nevertheless, the short range of the e lectron energy loss limits the contribution of these luminescent centers. C onsequently, the near-field/far-field contribution ratio in cathodoluminesc ence experiments is better than that of PL experiments done in the far-fiel d illumination/tip collection mode for which the far-field signal is more i mportant because of the large laser-beam excitation area. (C) 1999 American Institute of Physics. [S0021-8979(99)04220-6].