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

摘要

Trap states at the dielectric/GaN interface of AlGaN/GaN-based metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) cancause threshold voltage (V_(th)) instability especially under positive gate bias stress.Herein, the influence of O_2 plasma surface preconditioning (SPC) before theatomic layer deposition of the Al_2O_3 gate dielectric and of N_2 postmetallizationanneal (PMA) after gate metallization on the Al_2O_3/GaN interface quality isinvestigated. The interface is characterized by multifrequency capacitance–voltage measurements which show a smaller frequency dispersion after theemployment of SPC and PMA treatments with a reduction of the interface trapdensity D_(it) to a value in the order of 2 × 10~(12) cm~(-2) eV~(-1) near the conductionband edge. The effectiveness of SPC and PMA is demonstrated in Al_2O_3/AlGaN/GaN MIS-HEMTs by pulsed current–voltage measurements which revealimproved V_(th) stability.