The paper presents the results of capacitance measurements on GaN/AlGaNIGaN Schottky heterostructures grown on an Al2O3 substrate by Low-Pressure Metal-Organic Vapour-Phase Epitaxy (LP-MOVPE). Dependences of the capacitance-voltage (CV) characteristics on the frequency of the measuring signal allow analysing the properties of the 2D electron gas (2DEG) at the AlGaN/GaN heterojunction. Exact location of the hetero-interface below the surface (20nm) was determined from the concentration profile. Temperature variations of the CV curves reveal the influence of bulk defects in GaN and of the traps at the AlGaN/GaN interface. Electrical activity of these defects was characterized by capacitance Deep Level Transient Fourier Spectroscopy (DLTFS). Experimental results of CV measurements were supported by simulating the properties of the GaN/A10.2GaN0.8/GaN Schottky heterostructure in dependence on the influence of the concentration of donor-like traps in GaN and of the temperature upon the CV curves. (C) 2014 Elsevier B.V. All rights reserved.