Nominally undoped AlGaN / GaN heterostructure samples were grown on c-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition, and their material properties, such as crystal quality, roughness of heterointerface, thickness and Al mole fraction of AlGaN barrier layer, were identified by high resolution X-ray diffraction (HRXRD). Mercury-probe capacitance–voltage (C–V) measurements were carried out to investigate the carrier distribution in the heterostructures and accurately evaluate the sheet carrier concentration of two-dimensional electron gas (2DEG) formed at AlGaN / GaN heterointerface. The dependence of C–V characteristics of these samples on some key material parameters were clearly revealed. The Al -content effect, barrier-thickness effect in AlGaN layer, and their synergy effect were specifically studied. It demonstrated that the C–V characteristics of AlGaN / GaN heterostructure could be improved by perfecting the crystal epitaxial process, and adjusting the Al -content or thickness of AlGaN barrier layer.
Determination of Temperature-Dependent Stress State in Thin AlGaN Layer of AlGaN/GaN HEMT Heterostructures by Near-Resonant Raman Scattering