Local emission spectroscopy of surface micrograins in A$^{\mathrm{III}}$B$^{\mathrm{V}}$ semiconductors

The density-of-states spectra and the parameters of levels of electron states in locally chosen surface micrograins of indium antimonide and arsenide and gallium arsenide are studied with a tunneling electron microscope in the field-emission mode of measurements. By correlating the current–voltage characteristics with the formula for the probability of emission via levels, the activation energies of the levels $(\psi)$ and the lifetimes of electrons at the levels $(\tau)$ are determined. Two types of levels for electron localization are identified. These are levels in the micrograin bulk ($\psi\approx$ 0.75, 1.15, and 1.59 eV for $n$-InSb, $n$-InAs, and $n$-GaAs, respectively; $\tau\sim$ 10$^{-8}$–10$^{-7}$ s) and in the surface region of an $i$-InSb micrograin ($\psi\sim$ 0.73, 1.33, 1.85, 2.15, 5.1 eV; $\tau\approx$ 5 $\times$ 10$^{-8}$–3 $ \times$ 10$^{-7}$ s). A physical model involving the Coulomb-interaction-induced localization of light electrons and their size quantization determined by the electron effective mass, energy, and concentration and by the surface curvature of the micrograin is proposed.