Current oscillation in GaN-HEMTs with p-GaN islands buried layer for terahertz applications

A GaN-based high electron mobility transistor(HEMT)with p-GaN islands buried layer(PIBL)for terahertz applications is proposed.The introduction of a p-GaN island redistributes the electric field in the gate–drain channel region,thereby promoting the formation of electronic domains in the two-dimensional electron gas(2DEG)channel.The formation and regulation mechanism of the electronic domains in the device are investigated using Silvaco-TCAD software.Simulation results show that the 0.2µm gate HEMT with a PIBL structure having a p-GaN island doping concentration(Np)of 2.5×10^(18)cm^(−3)–3×10^(18)cm^(−3)can generate stable oscillations up to 344 GHz–400 GHz under the gate–source voltage(V_(gs))of 0.6 V.As the distance(D_(p))between the p-GaN island and the heterojunction interface increases from 5 nm to 15 nm,the fundamental frequency decreases from 377 GHz to 344 GHz,as well as the ratio of oscillation current amplitude of the fundamental component to the average component I_(f1)/I_(avg) ranging from 2.4%to 3.84%.

Effects of notch structures on DC and RF performances of AlGaN/GaN high electron mobility transistors

The effects of various notch structures on direct current(DC) and radio frequency(RF) performances of AlGaN/GaN high electron mobility transistors(HEMTs) are analyzed.The AlGaN/GaN HEMTs,each with a 0.8-μm gate length,50-μm gate width,and 3-μm source-drain distance in various notch structures at the AlGaN/GaN barrier layer,are manufactured to achieve the desired DC and RF characteristics.The maximum drain current(I_(ds,max)),pinch-off voltage(V_(th)),maximum transconductance(gm),gate voltage swing(GVS),subthreshold current,gate leakage current,pulsed I-V characteristics,breakdown voltage,cut-off frequency(f_(T)),and maximum oscillation frequency(f_(max)) are investigated.The results show that the double-notch structure HEMT has a 30% improvement of gate voltage swing,a 42.2% improvement of breakdown voltage,and a 9% improvement of cut-off frequency compared with the conventional HEMT.The notch structure also has a good suppression of the current collapse.