Theory of room temperature quantized resistance steps in electroformed metal-a-Si:H-metal structures

Previous work by Hajto et al. [J. Non-Cryst. Solids 137/138 (1991) 499; Phil. Mag. 66 (1991) 349], Yun et al. [Appl. Phys. Lett. 63 (1993) 2493] and Jafar and Haneman [Phys. Rev. B 47 (1993) 10911] has suggested quantized electron transport at high temperature in amorphous silicon V-p+-Cr devices. A feature of transport in these devices is a sequence of steps in the resistance-voltage characteristic which seem to be of integer or half integer multiples of h2e2 Ω, the voltage at which such jumps occur is non-periodic. Such observations conflict with other forms of ballistic channels [J. Phys. C 60 (1998) 848] which show single jumps of h2e2 Ω at periodic voltages. We present a simple model that shows that this difference arises as a natural consequence of having a two terminal geometry in which the applied electric field along the channel influences the number of conducting sub-bands instead of the electric field controlling the width of the channel.