Strain-dependent electron paramagnetic resonance and spin-valley coupling of shallow triplet Sn donors in GaP

We describe electron-paramagnetic-resonance studies of shallow tin donors in GaP under applied uniaxial stress. Because of the X3 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 gL. From the stress dependence of the resonance we have determined directly the one-valley g factors g=1.997±0.001 and g=1.991±0.003 and the intervalley g factor gL=0.010±0.002. This is the first time that these parameters are determined for GaP. In addition, we deduce the value (4.8 ± 0.7) × 10-4 for the rms value of random strain and 5.2 ± 0.4 eV for the deformation potential Ξu* of the bound state. © 1972 The American Physical Society.