Ultrasteep\nSlope Cryogenic FETs Based on Bilayer Graphene

Cryogenic field-effect transistors (FETs) offer great\npotential\nfor applications, the most notable example being classical control\nelectronics for quantum information processors. For the latter, on-chip\nFETs with low power consumption are crucial. This requires operating\nvoltages in the millivolt range, which are only achievable in devices\nwith ultrasteep subthreshold slopes. However, in conventional cryogenic\nmetal-oxide-semiconductor (MOS)FETs based on bulk material, the experimentally\nachieved inverse subthreshold slopes saturate around a few mV/dec\ndue to disorder and charged defects at the MOS interface. FETs based\non two-dimensional materials offer a promising alternative. Here,\nwe show that FETs based on Bernal stacked bilayer graphene encapsulated\nin hexagonal boron nitride and graphite gates exhibit inverse subthreshold\nslopes of down to 250 μV/dec at 0.1 K, approaching the Boltzmann\nlimit. This result indicates an effective suppression of band tailing\nin van der Waals heterostructures without bulk interfaces, leading\nto superior device performance at cryogenic temperature.