Analytical Modeling of Drain-Current Characteristics of AlGaN/GaN HFETs with Incorporation of the Impacts of Virtual-Gate and Transferred-Electron Effect

Analytical Modeling of Drain-Current Characteristics of AlGaN/GaN HFETs with Incorporation of the Impacts of Virtual-Gate and Transferred-Electron Effect Maziar Moradi GaN-based heterostructure field effect transistors (HFETs) have gained considerable attention in high-power microwave applications. So far, unsurpassed current levels and high output power at microwave frequencies have been achieved. However, the dominant factors limiting the reliability of these devices under high-power operation are still unsettled. Drain current collapse is one of the major encumbrances in the development of reliable high-power devices in this technology. In this thesis, an accurate and versatile analytical model based on the concept of virtual gate formation due to the existence of acceptor type surface states is developed to model the current-collapse phenomenon. The implementation of this simple and at the same time precise analytical model demonstrates superb agreement with the experimental observations of permanent/semi-permanent current collapse in AlGaN/GaN HFETs. An analytical model, with incorporation of transferred-electron effect, for draincurrent characteristics of AlGaN/GaN HFETs is also presented. Oftentimes, the transferred electron effect is neglected in modeling the drain-current characteristics of IIIV HFETs. The broader steady-state electron drift-velocity overshoot of GaN in comparison to other direct semiconductors such as GaAs and InP, in addition to the larger difference between the peak and saturation drift-velocity, and the wider bandgap of this