Surface Preconditioning and Postmetallization Anneal Improving Interface Properties and Vth Stability under Positive Gate Bias Stress in AlGaN/GaN MIS-HEMTs

Trap states at the dielectric/GaN interface of AlGaN/GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) can cause threshold voltage (V-th) instability especially under positive gate bias stress. Herein, the influence of O-2 plasma surface preconditioning (SPC) before the atomic layer deposition of the Al2O3 gate dielectric and of N-2 postmetallization anneal (PMA) after gate metallization on the Al2O3/GaN interface quality is investigated. The interface is characterized by multifrequency capacitance-voltage measurements which show a smaller frequency dispersion after the employment of SPC and PMA treatments with a reduction of the interface trap density D-it to a value in the order of 2 x 10(12) cm(-2) eV(-1) near the conduction band edge. The effectiveness of SPC and PMA is demonstrated in Al2O3/AlGaN/GaN MIS-HEMTs by pulsed current-voltage measurements which reveal improved V-th stability.

Automated summary

Preconditioning with O-2 plasma and postmetallization annealing with N-2 can effectively reduce trap states and improve interface quality at the Al2O3/GaN interface, leading to enhanced threshold voltage stability in AlGaN/GaN MIS-HEMTs.