Physical Theory of Semiconductor Surfaces

The properties associated with the space-charge region and with surface states at a semiconductor surface are discussed. A theory of the space-charge region that takes into account charge-densities arising from immobile impurities and from both signs of mobile carrier is presented. The properties of the space-charge are discussed in terms of the surface potential and of the electrochemical potentials of holes and electrons, and related to the transport of added carriers in a homogeneous semiconductor. The change in surface conductivity arising from nonvanishing surface excesses of holes and electrons is treated. The space-charge systems at a free surface and at a p-n junction are compared, and the range of validity of the Mott-Schottky space-charge theory evaluated. The arrangement of surface states is discussed with reference to the Brattain-Bardeen model. Theories for the surface photoeffect and field-effect experiments are given, with and without surface states: it is concluded that the existence of surface states is without gross effect on the former, while relevant quantitative evidence from the latter is not yet available. The question of the relation between surface potential and contact potential is discussed. The properties of "channels" are discussed in terms of the theory. The paper concludes with a short section on long-time effects.