Scaling and traps induced degradation of cutoff frequency in GaN HEMT

The effects of electric field induced traps generation in the drain access region is studied using industry standard TCAD, Atlas by Silvaco [1]. 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 E
_T
= E
_v
+ 0.9 (eV), corresponding to substitutional carbon in GaN, and a concentration of N
_IT
= 5 ×10
¹⁷
(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 [2].