Modeling and Design of Low Threshold Voltage D-mode GaN HEMT

Abstract

The wide energy gap of GaN is the major parameter justifying the design and fabrication of high-power electronic components made of this material. However, the existence of a sheet charge at the AlGaN/GaN interface complicates the control of carrier injection into the intrinsic channel of GaN HEMTs. As a result, most of the transistors created as R&D prototypes and all of the designs used for mass production are D-mode devices which introduce challenges in the design of integrated circuits. Our research presents the design and modelling of a GaN HEMT with a very low turn-on voltage. Another significant aspect associated with this design is the use of silicon substrate electrically isolated from the device by means of a thin layer of silicon nitride grown on top of the former. The flexibility of this nanostructure allows the amount of charge injected into the channel to greatly exceed the interface charge at the heterostructure interface. The transconductance of the device is about 23 mS/mm with a maximum gain of 24dB.