The piezoelectric photoacoustic effect of silicon wafers with ap/njunction in the dc electric field is studied experimentally and theoretically. Based on the transport properties of semiconductors, four kinds of thermal wave sources are considered: (i) instantaneous intraband nonradiative thermalization, (ii) interband nonradiative bulk recombination of photogenerated carriers (PGC), (iii) interband nonradiative surface recombination of PGC, and (iv) instantaneous Joule thermalization of PGC in the applied electric field. The theoretical results are in good agreement with those of experiment. Both show that the contribution of the Joule thermalization is a major factor and the photoacoustic signal will be strengthened as the dc electric field increases beyond an appropriate value. Therefore, the signal‐to‐noise ratio and the contrast of photoacoustic imaging of the semiconductor devices can be improved by the dc external electric field.