A review of recent experiments pertaining to hole transport in Si3N4

In spite of the recent accumulation of experimental evidence for hole conduction in Si3N4it has been largely ignored in modeling of MNOS devices, especially, when hole injection from the metal electrode should have been considered. A review of recent experiments related to hole conduction in Si3N4films deposited on silicon is given. The experiments include: photo-induced and dark and flat-band tracking; charge-centroid; and shallow junction "carrier-type" experiments. The case for hole conduction is established firmly for both polarities of applied voltage; however, while agreement exists that holes dominate the conduction for negative polarity (injection of holes from the silicon substrate), differences of opinion remain about the role of electron conduction under positive polarity. A comparison of the qualitative features of the valence band structure of Si3N4and SiO2is included to show that the same reason for low hole conduction in SiO2is not expected in Si3N4.