Lithium Donors and the Binding of Excitons at Neutral Donors and Acceptors in Gallium Phosphide
Two interstitial Li donors have heen identified in GaP through the photoluminescence spectra they induce. Donor A exhibits bound exciton and d-a pair luminescence with weak no-phonon lines and is shallow, ionization energy ED~56 meV, like a Ga-type donor. Donor B is deeper, ED = 88.3 ± 0.5 meV and generates strong no-phonon luminescence, like a P-type donor. Zeeman splittings of the lower energy bound exciton no-phonon line show that donor B has symmetry with <lll> axis, a novel situation for donor-exciton luminescence in GaP. The values of the exciton localization energy EBX for these shallow Li donors enable the trend of EBX vs. ED to be established firmly for the first time in GaP. Pronounced deviations from the Haynes’ rule form found in Si are noted and are given a qualitative interpretation in terms of a difference in the appropriate mass ratio me/mh for GaP and Si.
KeywordsNeutral Donor Phonon Replica Magnetic Splitting Gallium Phosphide Exciton Spectrum
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