P31nuclear magnetic shielding in group-III phosphide semiconductors

The ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ nuclear magnetic shielding (or chemical shift) of AIP at room temperature was determined by the Kunitomo first-moment method. With respect to an aqueous solution of ${\mathrm{H}}_3$P${\mathrm{O}}_4$ the shift is +33 ±4 ppm, corrected for bulk susceptibility effects. This result and previously reported shielding values for BP, GaP, and InP can be understood in terms of an approximate theory based on Harrison's bond-orbital method. The theory correctly gives the sign and order of magnitude of the shifts, but there remains some discrepancy between the observed and calculated values. A correlation between the chemical shift and the Szigeti effective charge, previously found by Lütgemeier for the heavier nuclei in the III-V compounds, is extended to ${}_{}{}^{31}{}_{}{}^{}\mathrm{P}$ nuclei in the group-III phosphides.