Photoluminescence of oxygen-passivated porous silicon analyzed by wideband quadrature frequency resolved spectroscopy

Wideband quadrature frequency spectroscopy (QFRS) reveals that the photoluminescence (PL) lifetime distribution of porous silicon (PS) is inherently double-peaked in structure. The main peak is the well-known S-band PL peak with a lifetime of a few tens μs at room temperature that changes to ∼ms at cryogenic temperature. The other is a smaller peak in the ∼ns lifetime region, which is enhanced by oxygen-passivation. The recombination rate vs. photoemission energy as well as PL spectrum of each component obtained for different temperatures and excitation energies indicates that the short-lived component is identified with so-called E-band PL arising from a quantum confined exciton. Further, the S-band PL peak originates from the recombination of a photo-carrier trapped in the surface state and its free partner (oppositely-charged carrier) in crystalline Si core of PS.