SPONTANEOUS POLARIZATION AND PIEZOELECTRIC CONSTANTS OF III-V NITRIDES

The spontaneous polarization, dynamical Born charges, and piezoelectri c constants of the III-V nitrides AlN, GaN, and InN are studied ab ini tio using the Berry-phase approach to polarization in solids. The piez oelectric constants are found to be up to ten times larger than in con ventional III-V and II-VI semiconductor compounds and comparable to th ose of ZnO. Further properties at variance with those of conventional III-V compounds are the sign of the piezoelectric constants (positive as in II-VI compounds) and the very large spontaneous polarization. [S 0163-1829(97)51740-1].