Surface recombination in doped semiconductors: Effect of light excitation power and of surface passivation

For n- and p-type semiconductors doped above the 1016 cm−3 range, simple analytical expressions for the surface recombination velocity S have been obtained as a function of excitation power P and surface state density NT. These predictions are in excellent agreement with measurements on p-type GaAs films, using a novel polarized microluminescence technique. The effect on S of surface passivation is a combination of the changes of three factors, each of which depends on NT: (i) a power-independent factor which is inversely proportional to NT and (ii) two factors which reveal the effect of photovoltage and the shift of the electron surface quasi Fermi level, respectively. In the whole range of accessible excitation powers, these two factors play a significant role so that S always depends on power. Three physical regimes are outlined. In the first regime, illustrated experimentally by the oxidized GaAs surface, S depends on P as a power law of exponent determined by NT. A decrease of S such as the one induc...