Abstract
Photoacoustic (PA) spectra near the energy gap (Eg) of n- and p-type silicon (Si) were observed at various carrier concentrations using a piezoelectric transducer method. With increasing carrier concentration, the PA signal intensity at energies slightly higher than Eg decreased for n-type samples and increased for p-type samples. The decrease and the increase were considered to be due to the increase in free electrons at the bottom of the conduction band and to the increase in holes at the top of the valence band, respectively. The PA spectra were not observed for either type of sample above a carrier concentration of 1017 cm-3.