Threshold voltage control of non-recessed GaN MOS HEMTs and recessed GaN MOS FETs by Al _x Ga_1−x N back barrier

Abstract

Threshold voltage (Vth) control of a GaN MOS transistor by AlxGa1−xN back barrier was systematically studied. Non-recessed GaN MOS HEMTs and recessed GaN MOS FETs with an AlxGa1−xN (x = 0%, 3%, 5%, 8%) back barrier layer were fabricated on the same 6 inch GaN-on-Si wafers and characterized. Al2O3 gate-insulator thickness was changed from 20 to 100 nm to evaluate the Al2O3/GaN interface fixed charge. The Vth of the GaN MOS transistor increases with increasing in Al content x of the AlxGa1−xN back barrier layer and decreasing in Al2O3 thickness. The dependences of Vth on Al content x and Al2O3 thickness were different between non-recessed and recessed transistor. The different dependences of Vth on Al content x and Al2O3 thickness were explained well by the newly introduced surface donor model, which compensate not only the surface polarization charge but also the surface electric field.

Investigation of Electrical Property and Thermal Stability in Enhancement-Mode InxAl1–xN/AlN/GaN MOS-HEMTs Fabricated by Using NiOx Gate and Fluorine Treatment

“…Converting Dmode to E-mode HEMTs is also desirable for the development of monolithic integrated functional circuits [4][5][6][7][8]. For conventional GaN-based HEMTs, various methods have been implemented to achieve Emode operation, including fluoride-based plasma treatment [4], Al x Ga 1-x N back barrier [9], different gate metallization [10], recessed gate [11] and p-type gate [12][13][14]. Nevertheless, when considering In x Al 1-x N/GaN heterostructure, the elevated 2-DEG density(~ 10 13 cm -2 ) arising from spontaneous polarization presents challenges for effective channel depletion.…”