Solid State Science and Technology, Vol. 15, No 2 (2007) 16-21
PHOTOACOUSTIC TECHNIQUE FOR MEASURING BAND-GAP ENERGY OF POROUS SILICON LAYER ON n-Si SUBSTRATE.
Chan Kok Sheng1, W. Mahmood Mat Yunus1, Wan Md. Zin Wan Yunus2,
Zainal Abidin Talib1 and Anuar Kassim2
1Department of Physics, 2Department of Chemistry
Faculty of Science
Universiti Putra Malaysia
43400 UPM Serdang, Malaysia.
The porous silicon layer was prepared on n-type Si wafers using electrochemical-etching method. The current density was varied from 16 mA/cm2 to 40 mA/cm2. The surface morphology measured using SEM confirms the formation of porous layer on the silicon substrate. The photoacoustic (PA) absorption band and optical band gap energy were determined from PA signal intensity spectra measured at three different modulation frequencies (i.e. 15 Hz, 23 Hz and 33 Hz). The absorption band and energy gap of porous silicon gradually shifted towards higher energy region as the increase of current density thus confirming the porosity dependence of band gap on sample porosity.
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