Second harmonic generation at a semiconductor–electrolyte interface and investigation of the surface of silicon by the nonlinear electroreflection method

A phenomenological theory is developed of the nonlinear electroreflection (NER), i.e., of the change in the intensity of a reflected second harmonic which occurs on application of an electrostatic field. An expression is obtained for the NER coefficient and in the case of a nondegenerate (in the space charge region) semiconductor an analysis is made of the dependences of this coefficient on such parameters of the reflecting surface as the oxide layer thickness, the density and energy of the surface states, the degree of doping, etc. A numerical experiment is reported for nondegenerate silicon and an investigation is made of changes in the NER curve due to the variation of the surface parameters. The results are given of an experimental study of the relationship between the second-harmonic intensity, on the one hand, and the surface charge and the surface oxide thickness, on the other. A good agreement is reported between the experimental and calculated results.