Surface Preconditioning and Postmetallization Anneal Improving Interface Properties and V th 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 Al 2 O 3 gate dielectric and of N 2 postmetallization anneal (PMA) after gate metallization on the Al 2 O 3 /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 × 10 12  cm −2  eV −1 near the conduction band edge. The effectiveness of SPC and PMA is demonstrated in Al 2 O 3 /AlGaN/GaN MIS‐HEMTs by pulsed current–voltage measurements which reveal improved V th stability.