Carrier concentration dependence of photoacoustic signal intensity of silicon

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