Abstract
We present transport measurements of silicon MOS split gate structures with and without Sb implants. We observe classical point contact (PC) behavior that is free of any pronounced unintentional resonances at liquid He temperatures. The implanted device has resonances superposed on the PC transport indicative of transport through the Sb donors. We fit the differential conductance to a rectangular tunnel barrier model with a linear barrier height dependence on source–drain voltage and non-linear dependence on gate bias. Effects such as Fowler–Nordheim (FN) tunneling and image charge barrier lowering (ICBL) are considered. Barrier heights and widths are estimated for the entire range of relevant biases. The barrier heights at the locations of some of the resonances for the implanted tunnel barrier are between 15–20 meV, which are consistent with transport through shallow partially hybridized Sb donors. The dependence of width and barrier height on gate voltage is found to be linear over a wide range of gate bias in the split gate geometry but deviates considerably when the barrier becomes large and is not described completely by standard 1D models such as FN or ICBL effects.
Highlights
Tunnel barriers formed using electrostatic gate structures are common experimental platforms for probing one-dimensional systems [1,2] including performing single impurity transport spectroscopy [3,4]
A similar linear dependence as well as similar magnitudes of U and w were predicted from a more complete semi-classical numeric simulation of the point contact geometry by Gao et al, the dependence was calculated for a plunger gate not the top Al gate [15]
The un-implanted Si MOS split gate conductance is free of resonant behavior at this temperature and shows contours of constant conductance that are qualitatively similar to those observed in split gate point contacts from other more model material systems (e.g., GaAs)
Summary
Tunnel barriers formed using electrostatic gate structures are common experimental platforms for probing one-dimensional systems [1,2] including performing single impurity transport spectroscopy [3,4] They are an essential building block for zero-dimensional lateral quantum dots [5]. MacLean et al developed a model that assumes a linear dependence of barrier height on gate and sourcedrain bias [7] and that fits experimental results for split gate tunnel barriers in GaAs and SiGe/sSi [8], at least for limited bias regimes. This linear dependence model could be used for this purpose. Understanding the role of high fields and geometry are important for the voltage ranges and split-gate geometry used for this form of single-shallow-boundimpurity spectroscopy [9]
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