Electronic structure of silicon nitride

Amorphous oxide SiO$_2$, oxynitride SiO$_x$N$_y$, and silicon nitride Si$_3$N$_4$ are the three key dielectric materials of silicon device technology. Silicon nitride is currently finding use in a variety of applications, in particular, as a storage medium in next-generation flash memory devices. Varying the chemical composition of nonstoichiometric silicon-rich SiN$_x$ allows a wide-range control of its optical and electrical properties. In this review, an analysis of the electronic structure of silicon nitride of varying composition is presented.