Carrier Concentration Dependence of Photoacoustic Signal Intensity of Silicon

Photoacoustic (PA) spectra near the energy gap of n- and p-type silicon were investigated at various carrier concentrations. The PA signal intensity at energies lower than the energy gap increased with increasing carrier concentration for both types. The increase is considered to be due to the increase in the heat generated in the samples following free carrier absorption and nonradiative relaxation processes. The PA signal intensity increased drastically above a carrier concentration of 10 17 cm -3 for n-type and above that of 10 16 cm -3 for p-type silicon.