A Rigorous Investigation of Electrostatic and Transport Phenomena of GaN Double-Channel HEMT

This paper presents a comprehensive investigation of electrostatics and transport characterization of GaN double-channel (DC) MOS-HEMT. Upon derivation of a polynomial analytical expression establishing a relationship between the Fermi level and the 2-D electron gas density (2DEG), a relationship between the sheet carrier density and applied gate voltage has been obtained. To confirm the validity of the model in both subthreshold and strong inversion regions, the charge density profile and capacitance-voltage profile have been attained from self-consistent simulation incorporating the quantum mechanical effect. The impact of GaN channel thickness on the conduction band profile as well as charge density profile has also been investigated. A 2-D analytical model for current-voltage characteristics of GaN-DC-MOS-HEMT has been developed for the first time. Assuming velocity saturation of electrons in 2DEG, the effects of spontaneous and piezoelectric polarization at the heterointerface, field dependent mobility, and the parasitic source and drain resistance have been taken into account in evolution of this model. The ON-resistance extracted from the analytical model was found to be 7.1 Omega.mm, which is in close proximity with experimental results. A steep subthreshold swing of 79 mV/dec was determined from the current-voltage characteristics with an ON-OFF drain current ratio of the order of 109, which holds the promising application for enhancement mode operation with minimal leakage current. For corroboration, the derived results were compared with experimental data acquired from the literature, thereby enhancing the reliability of this model.