OPTICAL-ABSORPTION IN POROUS SILICON STUDIED BY PHOTOACOUSTIC-SPECTROSCOPY

Nanoporous Si layers have been investigated by photoacoustic (PA) spec troscopy. The optical absorption spectra for porous Si on p-type Si su bstrates were obtained in the region of 300 to 1500 nm. The absorptivi ty became remarkable at 600 nm and increased drastically up to the sat uration value while the wavelength decreased from 500 to 300 nm. On th e basis of the comparison of photoacoustic spectra registered for diff erent light modulation frequencies the value of thermal conductivity o f porous Si was estimated to be 1.55 x 10(-3) W/(cm K).