| PhD Seminar

Name of the Speaker: Ms. A. V. Nandini Devi (EE18D028)
Guide: Prof. Shreepad Karmalkar
Co-Guide: Prof. Deleep R Nair
Online meeting link: https://meet.google.com/oqd-spza-mfp
Date/Time: 9th October 2024 (Wednesday), 9:00 AM
Title: Effect of Acceptor Buffer Traps on Contact Resistance in AlGaN/GaN HEMTs

Abstract :

As grown GaN buffer layers have a significant electron concentration, which causes an increase in leakage current and a decrease in the breakdown voltage of High Electron Mobility Transistors. To prevent this, deep acceptor traps of density, NAT, are added to the GaN layer during growth. While a study of the effect of NAT on breakdown is available in the literature, that on the effect of NAT on contact resistance, Rc, of source / drain contacts is lacking. We calibrated the TCAD simulator with the measured current-voltage characteristics of un-gated AlGaN / GaN structures where we found that default THERM model in ATLAS is not suitable for simulating Thermionic Emission currents, and that surface recombination velocity-based models should be used instead. From the TCAD simulations, we established the following: (i) Rc increases significantly with NAT and with the depth of the trap level from the conduction band. For trap level 2.5 eV below the conduction band, Rc doubles for an increase in NAT from 1×1016 cm-3 to 5×1017 cm-3. (ii) The variation of Rc with temperature is non-monotonic. Over a temperature range of 300 K to 450 K, Rc is nearly constant with temperature for NAT = 1 x 1016 cm-3 and decreases by 20% for NAT = 5×1017 cm-3, when traps are 2.5 eV below the conduction band.