Near IR and Visible Photoluminescence Studies of Porous Silicon

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Abstract
We report photoluminescence emission and photoluminescence excitation studies of porous silicon obtained from p-type Si(111) wafers over the range of 0.9–13.0 eV (∼400–1400 nm). Strong IR emission above and below the bulk silicon band gap at ∼1.09 eV (1135 nm) at 300 K was observed. This luminescence due to intrinsic band-to-band recombination, was found to be enhanced by two orders of magnitude or more over the IR spectrum from an unanodized wafer. The visible luminescence peak that has been attributed to quantum confinement effects in porous silicon was located at ∼1.8 eV (689 nm). We studied the high intensity IR and visible PL in detail as a function of temperature (4–700 K), laser excitation energy (1.96–3.80 eV), and laser power (0.1–1000 mW). The measured shift in the bulk silicon band gap was approximately linear from 300–700 K (∼−0.22 meV/K), while the visible peak red-shifted by ∼− 1.24 meV/K over the same range. Below 300 K they both had comparable temperature dependences. The visible PL was investigated at room temperature in magnetic fields up to 15 T; no discernible shift in the peak position or change in the peak intensity was observed.