The EPR and Luminescence of Porous Silicon

Abstract

The data on the EPR, photoluminescence (PL), and current transfer in porous silicon (PS) on KDB-0.3 and KES-0.01 Si, which was oxidized by 10-min isochronous thermal annealing in air at temperatures Tann from 20 to 900°C, as well as in HNO3, are presented in order to further clarify the nature of Pb centers of nonradiative recombination. The maximum PL quantum yield was observed during the chemical oxidation of PS on KDB-0.3 silicon. An anticorrelation of the PL and EPR intensities of Pb centers is observed in the range Tann = (20–300)°C. A nonmonotonic dependence of the EPR intensity of Pb centers on Tann with a minimum at approximately 700°C is revealed. The weak PL of PS with Tann of ~700°C accompanied by a minimum EPR signal from Pb centers means that other nonradiative-recombination centers arise after annealing. A decrease in the PS conductivity with an increase in Tann is associated with the decomposition of Si fibers in PS into small granules, through which discrete tunneling of current carriers occurs.