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Spectroscopic Investigation of Li and P-Doped ZnSe Grown by Molecular Beam Epitaxy
Published online by Cambridge University Press: 25 February 2011
Abstract
A conduction band-to-acceptor (e-A°) peak at 2.7060 eV has been identified for the first time in 1.7 K PL spectra of Li-doped ZnSe/GaAs. Photoluminescence (PL) measurements as a function of temperature and excitation level have been employed to confirm the identification and to study the behavior of this peak. This peak was previously misidentified as the “R”-band characteristic of bulk material, which has been associated with transitions between preferentially paired interstitial Li donors and substitutional Li acceptors on Zn sites. We find no direct evidence of Li interstitials in the PL data. The splitting of the Li acceptor-bound exciton is dramatically reduced by removal of the GaAs substrate, which proves that the splitting is due to strain and not to the hole-hole exchange interaction. A P-doped ZnSe/GaAs sample exhibits a shallow P bound exciton peak nearly superimposed on the donor-bound excitons. It is distinguished by its strong LO phonon replica and low energy undulation wing, which are both unique characteristics of shallow acceptor-bound excitons. Transitions involving the conduction band to split P acceptor light and heavy hole levels have been detected for the first time in P-doped heteroepitaxial ZnSe. Using the temperature dependence of the (e-A°) peak positions, accurate binding energies of 89.1±0.6 and 114.4±0.4 meV have been obtained for shallow P and Li acceptor levels in unstrained ZnSe, respectively
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- Copyright © Materials Research Society 1993