Gate-tunable graphene-based Hall sensors on flexible substrates with increased sensitivity

Abstract

We demonstrate a novel concept for operating graphene-based Hall sensors using an alternating current (AC) modulated gate voltage, which provides three important advantages compared to Hall sensors under static operation: (1) The sensor sensitivity can be doubled by utilizing both n- and p-type conductance. (2) A static magnetic field can be read out at frequencies in the kHz range, where the 1/f noise is lower compared to the static case. (3) The off-set voltage in the Hall signal can be reduced. This significantly increases the signal-to-noise ratio compared to Hall sensors without a gate electrode. A minimal detectable magnetic field Bmin down to and sensitivity up to 0.55 V/VT was found for Hall sensors working on flexible polyimide (PI) substrates. This clearly outperforms state-of-the-art flexible Hall sensors and is comparable to the values obtained by the best rigid III/V semiconductor Hall sensors.

Large-area integration of two-dimensional materials and their heterostructures by wafer bonding

“…The extracted sheet resistance and charge carrier mobility as a function of the gate voltage of a typical device (Fig. 3d , left) show the expected characteristic behavior of gated graphene devices 80 (see “Methods” for measurement details), where the mobility is zero at the Dirac point due to a zero of the transconductance. At this point, the charge carriers convert from electrons to holes or vice versa.…”

Graphene in 2D/3D Heterostructure Diodes for High Performance Electronics and Optoelectronics

“…[3,77,78] However, complex and costly growth of these III−V semiconductor materials and challenging CMOS fabrication line integration for mass production still leave room for further advantageous alternatives. [79] Graphene, [12] owing to its unique properties such as high mobility at room temperature [80,81] and broadband optical absorption [31,82] as well as its back-end-of-line (BEOL)-compatible CMOS integration scheme through transfer, [83,84] appears to be an ideal candidate for photo detection and 3D CMOS integration. [85][86][87] However, weak absolute optical absorption of graphene limits its photoresponsivity in many applications.…”

Optimizing the Stability of FETs Based on Two-Dimensional Materials by Fermi Level Tuning

“…When used in radio-frequency (RF) circuits the electric gate fields span from 3.5 MV/cm to 8.1 MV/cm [58][59][60][61] and thus the gate oxide fields we investigate here are standard operation conditions for RF applications. If on the other hand GFETs are used as sensors in the form of phototransistors 62,63 or Hall elements, 64 moderate gate fields of up to 1 MV/cm are sufficient to maximize responsivity.…”

“…GFET [2] GFET [3] GFET [4] Hall sensor [5] phototransistor [6] phototransistor [7] 57 and the ranges we use here are shown in purple below. Application scenarios are from [1], 60 [2], 61 [3], 59 [4], 58 [5], 64 [6], 62 [7]. 63 In (b) the hysteresis in the transfer characteristic measured on 5 different GFETs is shown, illustrating the variability of the devices.…”