|Publication Title||Scaling And Traps Induced Degradation Of Cut-off Frequency In GaN HEMTs|
|Publication Authors||B. C. Ubochi; S. Faramehr; K. Ahmeda; P. Igić; K. Kalna|
The effects of electric field induced traps generation in the drain access region is studied using industry standard TCAD, Atlas by Silvaco . We show that the reduction in the cut-off frequency of the device from 13.9 (GHz) to 11.25 (GHz) could be linked to the electric field induced traps. We have used acceptor traps at an energy level of ET = Ev + 0.9 (eV), corresponding to substitutional carbon in GaN, and a concentration of NIT = 5 ×1017(cm-3) to model the induced traps. Although vertical scaling has been used to reduce short channel effects, we observe that this leads to a reduction in the current arising from the reduced ionised surface donors .
|Publication Title||Operational Frequency Degradation Induced Trapping In Scaled GaN HEMTs|
|Publication Authors||Brendan Ubochi,Soroush Faramehr, Khaled Ahmeda, Petar Igić, Karol Kalna|
Cut-off frequency increase from 12.1 GHz to 26.4 GHz, 52.1 GHz and 91.4 GHz is observed when the 1 μm gate length GaN HEMT is laterally scaled down to LG = 0.5 μm, LG = 0.25 μm and LG = 0.125 μm, respectively. The study is based on accurately calibrated transfer characteristics (ID-VGS) of the 1 μm gate length device using Silvaco TCAD. If the scaling is also performed horizontally, proportionally to the lateral (full scaling), the maximum drain current is reduced by 38.2% when the gate-to-channel separation scales from 33 nm to 8.25 nm. Degradation of the RF performance of a GaN HEMT due to the electric field induced acceptor traps experienced under a high electrical stress is found to be about 8% for 1 μm gate length device. The degradation of scaled HEMTs reduces to 3.5% and 7.3% for the 0.25 μm and 0.125 gate length devices, respectively. The traps at energy level of ET = EV + 0.9 eV (carbon) with concentrations of NIT = 5 × 1016cm− 3, NIT = 5 × 1017cm− 3 and NIT = 5 × 1018cm− 3 are located in the drain access region where highest electrical field is expected. The effect of traps on the cut-off frequency is reduced for devices with shorter gate lengths down to 0.125 μm.