Energy and Lifetime of Space-Charge-Induced Localized States

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Abstract
The self-energy, density of states, and mobility of electrons in a narrow space-charge channel at an InAs surface are calculated, using a Green's-function method. A random array of contact potentials with a nonuniform average value is used to simulate the fluctuation potential due to irregularities at the surface and neutral defects. The use of a simple model for the solution to Poisson's equation determining the channel potential is justified by the sensitivity of the eigenvalues for motion normal to the channel to the local average value of the fluctuation potential. Therefore approximations used in estimating the fluctuation potential cause errors comparable to those due to a simplified treatment of the electrostatics. The two-dimensional character of the motion parallel to the channel results in (a) sharp steps in the imaginary part of the self-energy and concomitant sharp minima in the real part of the self-energy at the minima of the two-dimensional localized-state bands; and (b) energy shifts of the relatively sharp rises in the density of states at the bottom of each band.