Near Band Edge Photoacoustic Spectra of p-Si Single Crystals

Room-temperature photoacoustic (PA) spectra of p-type silicon single crystals were measured by using a piezoelectric transducer as a detector. Two peaks at 1.08 and 1.20 eV were observed. Since the peak at 1.08 eV appears only in boron-doped p-type samples, we consider this peak to be due to the boron impurity level. The 1.20 eV peak beyond the band gap observed for both p- and n-type samples is considered to be an apparent one due to the bending of the sample in the highly absorbing region. The effect of the modulation frequency and the detector geometries are explained well by taking into account the sample bending and the pyroelectric effect.