This paper presents a study of the vertical current transport in a graphene (Gr) heterostructure with Al x Ga 1-x N/GaN, which represent the main building block of a novel high frequency device, the hot electron transistor (HET) with Gr base. The morphological and electrical properties of this heterostructures have been investigated at nanoscale by atomic force microscopy (AFM) and conductive atomic force microscopy (CAFM). In particular, local current-voltage measurements by the CAFM probe revealed the formation of a Schottky contact with low barrier height (∼ 0.41 eV) and excellent lateral uniformity between Gr and AlGaN. Basing on the electrical parameters extracted from this characterization, the theoretical performances of a HET formed by a metal/Al 2 O 3/Gr/AlGaN/GaN stack have been evaluated.