Impulse response of piezoelectric photoacoustic signal in semiconductors

A theory of piezoelectric photoacoustic impulse response in semiconductors which takes into account the diffusion, lifetime, and surface recombination of the photogenerated carriers in addition to the thermal diffusion is discussed. It is shown that the impulse response changes considerably with the lifetime and the surface recombination velocity of photogenerated carriers. The impulse response has been measured for Si wafers with various surfaces, i.e. etched, sodium dichromate-coated and black painted. The impulse response depends strongly on the surface treatment, which indicates the importance of the diffusion and the surface recombination of photogenerated carriers in the analysis of the photogenerated carriers in the analysis of the photoacoustic impulse response of semiconductors.