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AlGaN/GaN FinMISHFETs with m-plane sidewall surface channel and various fin widths ($\text{W}_{\textsf {fin}}$) were fabricated and characterized. The investigated devices have much higher current drivability due to the uniform and smooth surface of m-plane than those with the a-plane sidewall surface channel. The AlGaN/GaN FinMISHFETs with $\text{W}_{\textsf {fin}}$ smaller than 36 nm exhibit normally-off operation, high Ion/Ioff ratio of 108, and remarkable subthreshold swing (SS) smaller than 40 mV/decade in the wide current range of at least three orders. Combined with a positive threshold voltage, SS values smaller than 60 mV/decade in a wide current rage of at least three orders are among the world’s best subthreshold characteristics. Furthermore, when $\text{W}_{\textsf {fin}}$ is 31 nm, the off-state drain current is as low as 10–12 A. We show that this sharp switch is due to the simultaneous turn-on of the 2-D electron gas and the m-plane sidewall surface channel. The simulation results are carried out to show the gate-induced variation of the electron concentration within the fin structure, and the assumption of considering gate width as a function of gate bias is also developed to explain the reason for deep sub-60mV/decade in the demonstrated devices. [ABSTRACT FROM AUTHOR]

AlGaN/GaN FinFETs with various fin widths ( W fin ), which have both a 2DEG channel and two sidewall MOS channels, have been fabricated by using electron-beam lithography and subsequent sidewall wet etch in tetramethyl ammonium hydroxide (TMAH) solution. The devices with wide W fin of 150 nm showed normally-on operation with threshold voltage ( V th ) of −2.5 and −5.0 V, respectively. The devices also exhibited broad transconductance ( g m ), and excellent off-state performance with very low subthreshold swing (SS). On the other hand, narrow device with W fin of 50 nm exhibited normally-off operation with V th of 3.0 V, but degraded SS due to trapping effect at the sidewall of fin. [ABSTRACT FROM AUTHOR]

In this paper, we have fabricated and investigated the AlGaN/GaN fin-shaped field-effect transistors (FinFETs) with and without TMAH surface treatment. DC and noise characteristics of the FinFETs were compared to evaluate the interface quality between Al 2 O 3 layer and the side-wall GaN surface. The tetramethyl ammonium hydroxide (TMAH)-treated device with a fin width of 70 nm and gate length, L g = 5 μm exhibited excellent device performances, such as drain current of 0.16 mA and transconductance ( g m ) of 0.11 ms, both 30% improved, and extremely small gate leakage current of about 10 −9 A at V gs = −5 V which is approximately two orders lower in magnitude compared to that of the device without TMAH treatment. Improved low-frequency noise performances were obtained for TMAH treated device due to the enhanced side-wall quality after the TMAH surface treatment. The trap density was found to be reduced approximately one order after TMAH treatment. Thus, simple surface treatment not only smoothens the sidewall surface but also eliminates the plasma damage caused during the fin etching, which leads to the reduction of trap density in AlGaN/GaN FinFETs. [ABSTRACT FROM AUTHOR]

AlGaN/GaN-based fin-shaped field-effect transistors with very steep side-wall have been fabricated by utilizing electron-beam lithography and subsequent anisotropic side-wall wet etch in tetramethyl ammonium hydroxide solution. The investigate device demonstrated extremely broad transconductance ( gm) ranging from \sim 0 to \sim 8 V at VD = 10 V, which is essential for high linearity device performance. Pulse measurement showed that the device exhibits negligible gate lag, but still suffers from drain lag. The device with L\mathrm {GD} of 17~\mu \textm exhibited excellent OFF-state characteristic with subthreshold swing of \sim 58 mV/decade, low OFF-state leakage current of \sim 10^{-12} A, and breakdown voltage of \sim 400$ V at V_{G}=- 9 V. [ABSTRACT FROM PUBLISHER]