Linear Polarization of Photoluminescence Excitation and Emission Spectra of Porous Silicon

Abstract

We have found a separation of the photoluminescence band caused by a strong spin-orbit splitting of holes in a porous silicon quantum well. The porous silicon has a red-orange photoluminescence (480 similar to 800 nm; lambda(max) about 600 mu) due to the quantum-confinement effect. In this research, the existence of sub-bands was newly confirmed by using the polarized excitation and photoluminescence spectroscopy. These sub-bands depended on the harmony of the rotation angle of the excitation and/or emission polarizers, respectively, and the degree of polarization was negative or positive values as a rotation angle of the excitation and emission polarizers. From these results, the quantum-confined band structure of the porous silicon is more concretely explained by using the spin-orbit splitting model. The photoluminescence band of the porous silicon was composed of an electron-heavy hole and electron-light hole recombination, and its relaxation process is in good agreement with the electron transition selection rule. Namely, the polarization of the nanoporous material is caused by a strong spin-orbit splitting of the quantum-confined valence band.