  Doped semiconductors are a central and crucial component of all integrated
circuits. By using a combination of white light and a focused laser beam, and
exploiting hBN defect states, heterostructures of hBN/Graphene/hBN are
photodoped in-operando, reproducibly and reversibly. We demonstrate device
geometries with spatially-defined doping type and magnitude. After each optical
doping procedure, magnetotransport measurements including quantum Hall
measurements are performed to characterize the device performance. In the
unipolar (p+-p-p+ and n-n+-n) configurations, we observe quantization of the
longitudinal resistance, proving well-defined doped regions and interfaces that
are further analyzed by Landauer-Buttiker modeling. Our unique measurements and
modeling of these optically doped devices reveal a complete separation of the
p- and n-Landau level edge states. The non-interaction of the edge states
results in an observed "insulating" state in devices with a bi-polar p-n-p
configuration that is uncommon and has not been measured previously in graphene
devices. This insulating state could be utilized in high-performance graphene
electrical switches. These quantitative magnetotransport measurements confirm
that these doping techniques can be applied to any 2D materials encapsulated
within hBN layers, enabling versatile, rewritable circuit elements for future
computing and memory applications.
