Impact of Gate and Drain Distance on Device Characteristics in InAlGaN/GaN High Electron Mobility Transistors

Abstract

The effect of the gate-drain distance (LGD) on device properties was examined in gallium nitride (GaN)-based high electron mobility transistors (HEMTs). We studied 70 nm gate length GaN HEMTs using a 7 nm-thick InAlGaN thin barrier, with LGD ranging from 1.3 to 2.6 μm. When we measured the typical device characteristics, the device performance in terms of the drain current and transconductance improved as LGD decreased. However, the short-channel effects (SCEs) were enhanced when LGD was reduced. By reducing LGD, the threshold voltage was negatively shifted and the subthreshold swing and drain-induced barrier lowering were increased, despite the 7 nm-thick InAlGaN barrier. To date, the SCEs have not been investigated in depth because GaN has a wide band-gap and strong immunity to electric fields. We conducted the electrical characterization of 70 nm gate length GaN-based HEMTs for the study involving SCEs with respect to LGD. Our systematic investigation revealed that SCEs occur even when a thin barrier is applied to GaN HEMTs. Additionally, detailed investigations for mitigating SCEs are required, as SCEs increase power consumption and deteriorate radio-frequency performance.