Nuclear-magnetic-resonance study of amorphous silicon-hydrogen-phosphorus alloys

${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$, ${}_{}{}^1{}_{}{}^{}\mathrm{H}$, and ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ nuclear-magnetic-resonance (NMR) spectra have been measured for hydrogenated amorphous silicon heavily doped with phosphorus (a-Si:H, P) as well as for undoped samples (a-Si:H). Phosphorus is enriched in the film during deposition. On the other hand, the hydrogen content is not changed very much by the phosphorus addition at a deposition temperature of 250 °C, while it increases very much at room temperature. In the samples deposited at 250 °C, most of the ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ spins have similar spin-lattice and spin-spin relaxation times and cross-polarization efficiencies. The ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ signal position is determined by chemical shift, and the linewidth includes negligible contribution from the dipole-dipole interaction, which indicates that most of the phosphorus atoms are bonded to neither hydrogen nor the other phosphorus atoms directly. The ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ linewidth is dominated by a chemical-shift dispersion of about 130 ppm, which suggests highly disordered structures. On the other hand, for the samples deposited at room temperature, the signal peak is shifted by -40 ppm with respect to the samples deposited at 250 °C, suggesting different bonding configurations. ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ NMR spectra reflect the hydrogen distribution in a-Si:H,P as well as a-Si:H, and the hydrogen distribution is changed by the phosphorus addition. The chemical-shift dispersion of ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ nuclei increases by the phosphorus addition at 250 °C because of the formation of Si–P bonds. On the other hand, the dispersion decreases at room temperature due to the relaxation of the structures caused by the incorporation of a large amount of hydrogen.