ABSTRACT
In this report, we have succeeded in suppressing the transconduction reduction by using Z1O 2 as a gate insulator.
2. Experiment Figure 1 shows a schematic cross section of the fabricated AlGaN/GaN MIS-HEMTs. The epitaxial layer structure consists of a 5-nm-thick undoped AlGaN barrier layer, a 15-nm-thick silicon doped Alo.25Gao.75N carrier supplying layer (« = 5><1018 cm'3), a 5nm-thick undoped AlGaN spacer layer, a 2-jim-thick GaN channel layer and LT-buffer layer grown on a sapphire substrate. The device was isolated by mesa etching using CI2 reactive ion etching. The ohmic contacts were formed by evaporating Ti/Al (20 nm/200 nm) and alloying at 650°C for 30 s in nitrogen atmosphere using a rapid thermal annealing (RTA) process. Following the ohmic contact formation, a Z1O 2 gate insulator (8 nm) was deposited by ECR sputtering (p-wave power: 500 W, RF power: 500 W).
