Strain-Dependent Electron Paramagnetic Resonance and Spin-Valley Coupling of Shallow Triplet Sn Donors in GaP

Abstract

We describe electron-paramagnetic-resonance studies of shallow tin donors in GaP under applied uniaxial stress. Because of the ${X}_{3}$ symmetry of the conduction-band minima relative to a Ga site, the Sn donor states are orbital triplets whose components correspond to the three valleys, with the sixfold degeneracy (including spin) split by a weak spin-valley coupling. The valleys are mixed also by the angular momentum operator of the Zeeman Hamiltonian with a small effective intervalley $g$ factor ${g}_{L}$. From the stress dependence of the resonance we have determined directly the one-valley $g$ factors ${g}_{\ensuremath{\perp}}=1.997\ifmmode\pm\else\textpm\fi{}0.001$ and ${g}_{\ensuremath{\parallel}}=1.991\ifmmode\pm\else\textpm\fi{}0.003$ and the intervalley $g$ factor ${g}_{L}=0.010\ifmmode\pm\else\textpm\fi{}0.002$. This is the first time that these parameters are determined for GaP. In addition, we deduce the value (4.8 \ifmmode\pm\else\textpm\fi{} 0.7) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ for the rms value of random strain and 5.2 \ifmmode\pm\else\textpm\fi{} 0.4 eV for the deformation potential ${\ensuremath{\Xi}}_{u}^{*}$ of the bound state.