2D-confined carrier systems have given access to the exploration of manifold quantum effects in fundamental research and also led to numerous device concepts for commercial electronic applications. Additionally, the possibility to control the 2D carrier density via gate voltages through the electric field-effect offers a great advantage of external manipulation of the system. With the optimization of lithography on a nanometre scale, gated 2D systems in semiconductor heterostructures are currently intensively studied as platforms for few to single-carrier devices. In this context, a precise control of the heterostructure layout including the doping, as well as an understanding of charge reconfiguration effects within the device, are important challenges.