Steps and spikes in current-voltage characteristics of oxide/ microcrystallite-silicon/oxide diodes

SiO₂/microcrystallite-Si/SiO₂ diodes with different contact window sizes were fabricated and studied at room temperature, 77 K, and 4.2 K. Steps were observed in the current-voltage (I-V) characteristics at all three temperatures. These steps would appear for a certain number of measurements, depending upon measurement temperature, and then were replaced by a smooth electrical breakdown I-V characteristic. Data analysis indicates that the steps in the I-V characteristics are due to local electrical breakdowns along the edge of metal contacts instead of electron resonant tunneling through the structure. Surprisingly, however, in one diode, three repeatable spikes, instead of steps, were observed at 4.2 K; this cannot be satisfactorily explained in terms of electrical breakdown, and seems rather like electron resonant tunneling.