On the Influence of Transistor Dimensions on the Dispersive Behavior in AlGaN/GaN HEMT-Based PAs and Robust LNAs
Trap-induced dispersive effects play an important role in PAs and robust LNAs based on AlGaN/GaN-HEMTs. In this paper, the influence of scaling gate-source (GS) and gate-drain (GD) separation is studied through pulsed DC measurements and TCAD physical device simulations. In view of PA-applications, dynamic on-resistance and drain current in the knee region after high drain voltage stress are investigated. The de-embedding of pure scaling effects shows that adverse effects due to trapping are largely independent of the transistor GS/GD separation. Likewise, with regard to robust LNAs, the shift of threshold voltage under large negative gate voltages, typical for RF input overdrive conditions, shows a strong dependence on quiescent stress, but not on device scaling. This is in line with TCAD physical device simulations which suggest that trapping of electrons as well as the extension of the depletion region is affected mainly by the heterostructure and trap properties but not GS or GD separation. The findings aid RF designers to optimize the performance and reliability of GaN-MMICs for the specific application.