A prototype of RK/200 quantum Hall array resistance standard on epitaxial graphene

Abstract

Epitaxial graphene on silicon carbide is a promising material for the next generation of quantum Hall resistance standards. Single Hall bars made of graphene have already surpassed their state-of-the-art GaAs based counterparts as an R K /2 (R K = h/e 2 ) standard, showing at least the same precision and higher breakdown current density. Compared to single devices, quantum Hall arrays using parallel or series connection of multiple Hall bars can offer resistance values spanning several orders of magnitude and (in case of parallel connection) significantly larger measurement currents, but impose strict requirements on uniformity of the material. To evaluate the quality of the available material, we have fabricated arrays of 100 Hall bars connected in parallel on epitaxial graphene. One out of four devices has shown quantized resistance that matched the correct value of R K /200 within the measurement precision of 10 −4 at magnetic fields between 7 and 9 Tesla. The defective behaviour of other arrays is attributed mainly to non-uniform doping. This result confirms the acceptable quality of epitaxial graphene, pointing towards the feasibility of well above 90% yield of working Hall bars.

Epitaxial Graphene on SiC: A Review of Growth and Characterization

“…One out of four devices has shown quantized resistance that matched the correct value of R-K/200 within the measurement precision of 10(-4) at magnetic fields between 7 and 9 T. The defective behavior of other arrays is attributed mainly to non-uniform doping. This result confirms the acceptable quality of epitaxial graphene, pointing towards the feasibility of well above 90% yield of working Hall bars [130]. Quantum Hall resistance measurements with metrological accuracy in a small cryogen-free system operating at a temperature of around 3.8 K and magnetic fields below 5 T, using a system that does not require an advanced skill set or infrastructure and so can proliferate easily, has been demonstrated [131].…”

Operation of graphene quantum Hall resistance standard in a cryogen-free table-top system

“…so that the operational parameters of all QHR devices overlap and all contacts need to be low ohmic. Recently, the first SiC/G quantum Hall array at R K /200 has been demonstrated [31]. Dissemination and proliferation of primary quantum standards is one of the key objectives of fundamental metrology.…”

Atypical quantized resistances in millimeter-scale epitaxial graphene p-n junctions

“…One approach to reaching this goal includes creating quantum Hall arrays. [17][18][19] A major disadvantage to this approach is the requirement that many individual Hall bar devices be connected using a network of resistive interconnects, thereby increasing the total minimum device size and possibly lacking optimal contact resistances. The second approach involves building p-n junctions (pnJs) that operate in the quantum Hall regime, as has been previously demonstrated in EG with lateral dimensions on the order of 100 μm.…”