The hot electron transistor (HET) is an unipolar majority carrier vertical device with great potential for high frequency (THz) applications. Recently, graphene (Gr) heterostructures with Nitrides have been considered as a promising material system to implement this device concept, with GaN/AlGaN (or GaN/AlN) working as emitter/emitter‐base barrier and Gr as the ultrathin base enabling ballistic transit of hot electrons. In this work, the main issues related to the fabrication of Gr/Nitrides heterojunctions are discussed. An optimized transfer procedure of large‐area Gr membranes onto AlGaN/GaN grown on Si(111) is illustrated. In particular, a soft O2 plasma pretreatment of the AlGaN surface is found to greatly improve the Gr adhesion, resulting in a reduced cracks density. A nanoscale electrical characterization of the obtained Gr/AlGaN/GaN heterostructures was carried out by conductive atomic force microscopy, to …