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AlGaN/GaN-based fin-shaped field-effect transistors (FinFETs) with very steep sidewall and various fin-widths (Wfin) have been fabricated by utilizing electron-beam lithography and additional anisotropic sidewall wet etch in TMAH solution. The device with Wfin of 150 nm exhibits normally-on performance with threshold voltage of -2.5 V, suppression of current collapse phenomenon, low gate leakage current (10 -11 A), low subthreshold swing (SS) of 68 mV/decade, and high linearity characteristic with extremely broad transconductance (gm). On the other hand, devices with Wfin = 50 and 70 nm exhibit normally-off performance with positive threshold voltage of 3.0 and 1.5 V, respectively, and less broad gm characteristics.I.

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The AlGaN/GaN nanowire omega-shaped-gate FinFET have been successfully fabricated demonstrating much improved performance compared to conventional AlGaN/GaN MISHFET. The AlGaN/GaN omega-shaped-gate FinFET exhibited the remarkable on-state performances, such as maximum drain current of 1.1 A/mm, low on-resistance, and low current collapse compared to that of the conventional device structure. In addition, the excellent off-state performances were measured: low off-state leakage current as low as -10(-10) mA, the theoretical SS value of -62 mV/dec, and high I(ON)/I(OFF) ratio (-10(9)). Improved dc performances were obtained for omega-shaped-gate structure due to the fully depletion of the active fin body and perfectly separation of the depleted fin from the underlying thick GaN buffer layer. Furthermore, the additional reason for the enhanced device performance of the proposed device is the improved gate controllability compared to the conventional MISHFET. The proposed nano-structure device is very promising candidate for the steep switching device applications.