Evaluation of on-state resistance in gallium nitride based power electronic switches

Gallium nitride (GaN) based high-electron-mobility transistor (HEMT) is getting popular in power electronics applications due to its low on-state resistance and superior switching characteristics. The on-state resistance of the switch is an important factor in the efficiency of the GaN switch based power converter. Firstly, the basic principle of operation of a normally-on GaN/AlGaN HEMT is reviewed. Then parallelization of several basic HEMT units internally to form a multi-finger-structured GaN device to achieve high current rating is illustrated. Later, estimation of the on-state resistance of a given device based on its internal structure and composition is attempted. Further, the variations in on-resistance with thickness of metalization of drain and source pads, length of the drain and source fingers, and the sheet resistance of two-dimensional electron gas (2DEG) are studied. This study on on-state resistance is used to provide architecture-level inputs to the design of a multi-finger GaN device for power electronics applications.