Scalable Electronic Ratchet with Over 10% Rectification Efficiency

Abstract

Electronic ratchets use a periodic potential with broken inversion symmetry to rectify undirected (electromagnetic, EM) forces and can in principle be a complement to conventional diode‐based designs. Unfortunately, ratchet devices reported to date have low or undetermined power conversion efficiencies, hampering applicability. Combining experiments and numerical modeling, field‐effect transistor‐based ratchets are investigated in which the driving signal is coupled into the accumulation layer via interdigitated finger electrodes that are capacitively coupled to the field effect transistor channel region. The output current–voltage curves of these ratchets can have a fill factor >> 0.25 which is highly favorable for the power output. Experimentally, a maximum power conversion efficiency well over 10% at 5 MHz, which is the highest reported value for an electronic ratchet, is determined. Device simulations indicate this number can be increased further by increasing the device asymmetry. A scaling analysis shows that the frequency range of optimal performance can be scaled to the THz regime, and possibly beyond, while adhering to technologically realistic parameters. Concomitantly, the power output density increases from ≈4 W m−2 to ≈1 MW m−2. Hence, this type of ratchet device can rectify high‐frequency EM fields at reasonable efficiencies, potentially paving the way for actual use as energy harvester.

Ratchet based ion pumps for selective ion separations

“…The symmetry breaking required to produce a directed current is achieved by structuring the gating electrodes, [13][14][15][16][17] introducing a nonlinear, diode like conductance between the source and drain, 18,19 or by applying different signals to different sets of gating electrodes. [20][21][22][23][24][25][26] Fig. 1a shows a schematic illustration of the operating principles of a flashing ratchet driving positive charge.…”

“…The asymmetric potential distribution allows some particles to reach the potential minima in one direction before particles drifting in the opposite direction, thus making it essential for a non-zero net current. While in most prior studies flashing rachets were used to drive electrons or holes in semiconductors, 13,14,[23][24][25][26][15][16][17][18][19][20][21][22] the application of flashing ratchets for ion pumping was only suggested recently. Membranes with oscillating pores for resonant osmosis were theoretically analyzed in terms of ratchet driven transport 28,29 and nanofluidic charge coupled devices, which can be viewed as reversible ratchets, 30 were studied for DNA separations.…”