Investigation on effect of AlN barrier thickness and lateral scalability of Fe-doped recessed T-gate AlN/GaN/SiC HEMT with polarization-graded back barrier for future RF electronic applications

Abstract

In this study, the influence of AlN barrier thickness (tb) on the RF & DC performances of 50 nm recessed T-gate Fe-doped AlN/GaN/SiC HEMT is investigated. The proposed HEMT incorporates a graded back-barrier (GBB) feature that raises the conduction band (CB) discontinuity at GaN/AlGaN junction to increase carrier confinement. With excellent electron confinement, the electrical characteristics for a 6 nm AlN barrier thickness show the highest transconductance of 468.9 mS/mm, a maximum ID of 1.546 A/mm, and a peak fT of 355 GHz at VDS = 2.5 V due to better epitaxial quality, and a reduction in parasitic channel generation due to GBB. When tb increases, the Vth decreases or becomes more negative i.e., moves left, which causes the ID to fall and degrades performance. This study also examines the influence of gate metals on the electrical performance of the proposed HEMT. According to the TCAD results, Pt-gate HEMTs had better RF performance. Furthermore, the simulation performed to examine the effects of scaling source-drain spacing (LSD) showed that the key to improving RF/DC performance is to reduce gate-to-drain and gate-to-source distances. It has been observed that the electron velocity of the HEMT is significantly influenced by the barrier thickness, LGS, and LGD. It comes as no surprise that this technology will be at the frontlines of future RF power applications.