NiO gate GaN-based enhancement-mode hetrojunction field-effect transistor with extremely low on-resistance using metal organic chemical vapor deposition regrown Ge-doped layer

In this paper, we present a normally-off GaN-based transistor with an extremely low on-resistance (R-on) fabricated by using a Ge-doped n(++)-GaN layer for ohmic contacts. We developed a novel GaN regrowth technique using Ge as a dopant, which achieved an extremely high doping concentration of 1 x 10(20)cm(-3), and thereby the lowest specific contact resistance of 1.5 x 10(-6) Omega.cm(2). The NiO gate fabricated using an atomic layer deposition technique reduced the spacing between the source and drain electrodes. The fabricated device showed the record-breaking R-on of 0.95 Omega mm with the maximum drain current and transconductance of 1.1A/mm and 490mS/mm, respectively. Note that the obtained threshold voltage was 0.55V. This extremely low R-on characteristic indicates the great potential of NiO-gate GaN-based heterojunction field-effect transistors. (C) 2016 The Japan Society of Applied Physics