Effect of access region and field plate on capacitance behavior of GaN HEMT

Incorporation of Field Plate in High Electron Mobility Transistors (HEMTs) improves the device breakdown voltage but on the other hand, increases the device Capacitance. It has a direct impact on the device switching characteristics and hence the study of the capacitive behavior holds supreme importance for GaN HEMTs power switching application. Also, in GaN HEMTs, lower values of access region resistance improves the device output current but at the cost of increase in its capacitance, C_GD. In this paper, using TCAD simulations on a field plated GaN HEMT, we present the physical explanation for the variation in C-V characteristics for different access region and field plate lengths.