Investigation of Field Plate Misalignment on Electrical Characteristics of AlGaN/ GaN HEMT

Abstract

Simulation based comprehensive analysis of aigan/GaN Field Plate HEMT has been reported in this paper. The impact of doping levels of GaN cap layer (either p-type or n-type) and lateral misalignment of field plate and its effect on device performance like off-state breakdown voltage, I ON /I OFF ratio, transconductance and cut-off frequency has been presented. Improvement in off-state breakdown voltage has been seen from the device having thicker channel with n-cap doping and negative FP misalignment length. Enhancement in n-cap doping also results in the improvement in breakdown voltage. However reverse effect has been observed with p-cap layer. Irrespective of poor off-state breakdown voltage, higher I on /I off ratio, lower sub-threshold slope and better transconductance can be achieved with FP-AIGaN/GaN having thinner channel HEMT. But the cut-off frequency deteriorates with reduction in channel thickness at lower gate voltage (-5V). Lateral FP misalignment and cap layer type and doping has marginal influence on gate to source capacitance. ATLAS Silvaco software has been used to investigate various performance of the device at room temperature.