On the photoacoustic characterization of semiconductors: Influence of carrier recombination on the thermodiffusion, thermoelastic and electronic strain signal generation mechanisms

A quantitative study of the photoacoustic (PA) signal dependence on the mod ulation frequency in semiconductors was performed. The carrier recombinatio n processes were taken into account to calculate the PA signal, considering the thermodiffusion (TD), thermoelastic (TE) and electronic strain (ES) si gnal generation mechanisms. Analytical expressions for these contributions and for the total pressure in the PA gas chamber are given for the heat tra nsmission detection configuration. The theoretical results were compared wi th measurements in Si samples, showing a good agreement. An anomalous behav ior of the PA signal dependence on the modulation frequency can only be exp lained, if the ES contribution is added to the other ones.