An investigation on the effect of porosity on the transport properties of porous silicon

摘要

Microelectronics technology today is dominated exclusively by Silicon (Si). The inefficiency of Si to emit light even at cryogenic temperatures has been overcome with the discovery of porous silicon (PS) and its visible luminescence at room temperature. The present investigation aims at analysing the effect of increasing porosity on the transport properties of porous silicon with reference to field and temperature-dependent dark and photo conductivity and further substantiating the results with modulation techniques. Pure Silicon wafer of n-type was made porous by immersion in an appropriate etchant for a few minutes. The conductivity was found to increase as porosity increased and this effect could be attributed to the increase in the trap levels, with increasing porosity. Temperature-dependent studies reveal a decrease in activation energy with increase in porosity indicating an increase in conductivity. Reflectance and electroreflectance measurements were used to calculate the band gap of porous silicon. It was found to lie closer to the direct band gap of silicon. A reduction in the band gap of porous silicon has been observed.