Continuous-wave (cw) electron paramagnetic resonance (EPR) at both X -band and W -band frequencies, pulsed-EPR, and pulsed electron nuclear double resonance (ENDOR) were used to study phosphorus shallow donors in 3C -, 4H -, and 6H-SiC doped with phosphorus (P) during chemical vapor deposition (CVD) growth. In 3C-SiC, a spectrum with D2d symmetry and the principal g values, g =2.0051, g =2.0046, was detected. The P31 hyperfine (hf) constants of the center, A =0.53 MHz and A =-0.13 MHz, were determined from pulsed-ENDOR measurements. A doublet with C3v symmetry (g =2.0065, g =2.0006, and P31 hf constants A =8.24 MHz, A =5.89 MHz) was detected in P-doped 4H-SiC. In the 6H polytype, the same P1 and P2 doublets [Greulich-Weber, Phys. Status Solidi A 162, 95 (1997)] or d Ph, d Pc1, and d Pc2 doublets [Baranov, Phys. Rev. B 66, 165206 (2002)] previously reported in material doped with P by neutron transmutation were detected. Our cw-EPR, two-dimensional EPR, and electron spin-echo envelope modulation (ESEEM) results confirm that the d Pc1 and d Pc2 doublets are related to different allowed and forbidden transitions of the P2 center with S=1 2 and I=1 2. Based on the observed P31 hf interaction (for three polytypes) and the C13 hf interaction with nearest neighbors (for 4H - and 6H-SiC), the P-related spectra are assigned to the ground states of the isolated shallow P at Si site. The valley-orbit splitting of the shallow P donors was estimated from the temperature dependence of the spin-lattice relaxation time and of the cw-EPR signal intensities. Based on the ab initio supercell calculations of the spin localizations on the P atom and the nearest C neighbors in 4H-SiC and the similarity between the spectra in the 4H and 6H polytypes, we reassign the spectrum in 4H-SiC to the shallow P donor at the quasicubic site (Pk) and the two doublets P1 and P2 in 6H-SiC to the shallow P donors at two quasicubic sites, Pk1 and Pk2, respectively. © 2006 The American Physical Society.
2006. Vol. 73, no 7