Properties of shallow Li-related donors in GaP from optically detected magnetic resonance

Optical detection of magnetic resonance (ODMR) via photoluminescence is demonstrated to be a powerful technique for the study of magnetic properties of shallow bound electron states in GaP. Two interstitial shallow Li-related donors, LiA and LiB, are studied in this work with the ODMR technique. The LiA donor has a binding energy of {}59 meV and an isotropic g factor of gₑ=1.99±{}0.01. The ODMR spectrum is easily observed without external stress, indicating that the corresponding interstitial site is distorted from the Ga-like tetrahedral site to a symmetry lower than trigonal. The LiB donor (binding energy {}91 meV) has a quite similar isotropic g value gₑ{}1.99±{}0.01, as expected in a P-like tetrahedral interstitial site, slightly distorted along the trigonal axis. Excitation transfer effects are conveniently detected via the spectral behavior of the ODMR signal, and are found to occur frequently in GaP. An interesting observation is an anisotropic donorlike resonance in (Cu-Li)-doped GaP, believed to be associated with an electron bound as a secondary particle at the hole-attractive neutral (Cu-Li)III complex defect at 2.242 eV. Transfer effects are found to cause linewidth narrowing in ODMR donor signals, which usually are considerably broader than those obtained in the conventional EPR technique.