Sapan Agarwal, Eli Yablonovitch
Tunneling based field effect transistors (TFET's) have the potential for very sharp On/Off transitions if they exploit a sharp step in the density of states for switching. The same principle applies in Backward Diodes. As is well-known, the nature of the quantum density of states, is strongly dependent on dimensionality. Hence we need to specify both the n-side and the p-side dimensionality of pn junctions. For instance, we find that a typical bulk 3d-3d tunneling pn junction has only a quadratic turn-on function, while a pn junction consisting of two overlapping quantum wells (2d-2d) would have the preferred step function response. Quantum confinement on each side of a pn junction has the added benefit of significantly increasing the on-state tunnel conductance at the turn-on threshold. We find that there are nine physically distinguishable possibilities, 3d-3d, 2d-3d, 2d-2d, etc. Thus we introduce the obligation of specifying the dimensionality on either side of pn junctions.
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http://arxiv.org/abs/1109.0096
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