Contact currents in silicon nitride

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Abstract
Simultaneous dark‐current and flat‐band–voltage measurements on metal‐Si3N4‐Si capacitors were used to deduce Si‐Si3N4 contact‐current–contact‐field characteristics under positive and negative voltage bias. Whereas total‐current–average‐field characteristics are functions of counterelectrode material and nitride thickness, these contact‐current–contact‐field characteristics were dependent solely on the local properties of the Si‐Si3N4 interface. Fowler‐Nordheim analysis of the contact characteristics assuming 2‐eV barrier heights as determined by internal photoemission indicated low effective masses of 0.05–0.13m0 for electrons and 0.005m0 for holes. Alternatively, use of an effective mass of 0.4m0 (as observed in SiO2) led to effective barrier heights of 0.8–1.2 eV for electrons and 0.44 eV for holes. Several mechanisms, including trap‐assisted tunneling, are discussed which could account for different dark‐current and photoemission barrier heights. In addition, simultaneous photocurrent and flat‐band–voltage measurements as a function of voltage bias were performed to assist in determining the dominant photocurrent carrier type (electrons or holes) and the limiting photocurrent mechanism (contact or bulk).