SOME EFFECTS OF MOBILE DONORS ON ELECTRON TRAPPING AT SEMICONDUCTOR SURFACES

A treatment of the surface energy barrier is given for n-type semicond uctors in the case of mobile donors. We consider finite grains and sol ve the Poisson-Boltzmann equation, related to the problem, for one-dim ensional (slab shape), two-dimensional (cylindrical-rod shape) and thr ee-dimensional (spherical shape) grain geometries. Analytical solution s are given for the band bending and surface energy barrier in one- an d two-dimensional grain geometries in the case of total grain depletio n, and a numerical approach was used to calculate the results in spher ical grains and also in partially depleted grains. Tin dioxide is used as an example to illustrate grain depletion in ambient oxygen atmosph ere in the case of mobile oxygen-vacancy donors.