Current saturation and steep switching in graphene PN junctions using angle-dependent scattering

Mirza M. Elahi, and A. W. Ghosh, 74th Device Research Conference (2016).
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Abstract

Graphene’s ultra-high carrier mobility ( $$200,000cm^2/Vs$$ on hBN) [1] makes it promising for high speed applications; however the absence of a band-gap makes it hard to design logic elements out of graphene. It is possible to open a bandgap in graphene by applying strain [2] or by confining it in one direction into nanoribbons [3], but in the process bandstructure gets distorted near Dirac point and the carrier mobility decreases [4]. A recent set of papers have exploited instead the angle dependent transmission across graphene pn junctions (GPNJ) [5-9]. Since the opening angle is gate tunable, a sequence of angled junctions can turn off the electrons [10,11] using gateable momentum filtering in the absence of a band-gap (instead, the ideas use a transmission gap). In the absence of edge scattering, momentum filtering is predicted to give large ON, low OFF current and a steep subthreshold swing (SS). In this paper, we calculate the transfer (ID–VG) and output (ID–VD) characteristics of a GPNJ switch [11] and show current saturation using gate geometry alone.