Metal-semiconductor-metal diodes have been fabricated using a range of dilute a - SiNx:H alloys. Current transport in unstressed devices was dominated by thermionic-field emission of electrons through the reverse biassed metal-semiconductor contacts with a tunnelling effective mass ≈0.1me. The barriers to electrons were strongly pinned by bulk states and scaled almost linearly with optical band gap.
Under high current stress, defect states were created below the Fermi level forming a -ve charge that changed the effective barrier height and produced drift in the current voltage characteristic. Unipolar stress measurements showed that this effect was related to hole transport. After prolonged stress the electrical characteristics were dominated by bulk effects due to the high density of metastable defects in the band gap.