Fourier-transform photoluminescence spectroscopy of excitons bound to group-III acceptors in silicon: Zeeman effect.

Abstract

Photoluminescence of excitons bound to Al, Ga, In, and Tl acceptors in Si was studied at liquid-He temperatures in magnetic fields up to 14.5 T with 〈001〉, 〈111〉, and 〈110〉 orientations with 0.0025-meV spectral resolution. All details of the Zeeman spectra for every field orientation, with up to 30 resolved spectral components, have been explained on the basis of a simple model of acceptor bound excitons with holes in a singlet state J=0. The variation of the electron valley-orbit splitting of the bound exciton energy levels in magnetic fields was used for unambiguous identification of the zero-field valley-orbit state ordering. An additional 0.02-meV splitting of the ${\mathrm{\ensuremath{\Gamma}}}_{5}$ bound exciton energy levels due to spin-orbit coupling was observed for In bound excitons. The amplitude ratios in polarized Zeeman spectra agree with selection rules derived on the basis of the shell model. The ratios of the selection rule constants determined from the zero-field spectra indicate that hole scattering is responsible for no-phonon optical transitions in acceptor bound excitons. The electron spin and valley-orbit relaxation times were estimated to be longer than 3 ns and shorter than 76 ns on the basis of nonthermal population of the excited In and Tl bound exciton energy levels and complete thermalization of the Al and Ga bound excitons. \textcopyright{} 1996 The American Physical Society.