Conditions for population inversion in surface-barrier structures

The contact of a metal with a p-type semiconductor is discussed. Formulation is given of the conditions that the work function of the metal, characteristics of the surface states, and concentration of the dopant in the semiconductor must satisfy to achieve a population inversion in such a metal-semiconductor structure when the potential barrier is suppressed. A more general condition for the amplification of light in an ideal Schottky barrier is discussed also in the case of a high density of surface states. Numerical estimates are obtained for several p- and n-type semiconductors.