Characteristics Improvement of AlGaN/GaN MOS-HEMT by Thickness and Doping Concentration Variation of GaN Doped Layer

This paper presents a method to precisely control the device characteristics, i.e. the threshold voltage and the transconductance of AlGaN/GaN metal oxide semiconductor high electron mobility transistors (MOS-HEMTs) by varying doping concentration and thickness of GaN doped layer. Mode of operation of the device can be changed from conventional depletion-mode (D-mode) HEMT to enhancement-mode (E-mode) HEMT at a drain-source bias of 4V. However, to achieve the condition of E-mode HEMT, two dimensional electron gas (2DEG) density has to be depleted from channel. As a result, the device suffers from reduced drain current density as well as high on resistance. To reduce the access resistance and improve transconductance, doping concentration and thickness of GaN doped layer are increased. The proposed E-mode AlGaN/GaN MOS-HEMT device has exhibited excellent device performance by achieving higher transconductance, positive threshold voltage, and high drain current density.