Browsing by Subject "FinFET"

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Open Access
AlGaN/GaN-Based laterally gated high-electron-mobility transistors with optimized linearity
(IEEE, 2021-02-01) Odabaşı, Oğuz; Yılmaz, Doğan; Aras, Erdem; Asan, Kübra Elif; Zafar, Salahuddin; Çankaya Akoğlu, Büşra; Bütün, Bayram; Özbay, Ekmel
In this work, highly linear AlGaN/GaN laterally gated (or buried gate) high-electron-mobility transistors (HEMTs) are reported. The effect of gate dimensions on source-access resistance and the linearity of laterally gated devices are investigated experimentally in detail for the first time. Transistors with different gate dimensions and conventional planar devices are fabricated using two-step electron beam lithography (EBL). Current-voltage, source-access resistance, small-signal, and two-tone measurements are performed to evaluate the linearity of devices. Contrary to conventional planar HEMTs, the intrinsic transconductance of laterally gated devices monotonically increases with increasing gate voltage, showing a similar behavior as junction field-effect transistors (FETs). The source-access resistance shows a polynomial increase with the drain current, which can be reduced by decreasing the filling ratio of the buried gates. Through the optimization of these two competing factors, i.e., intrinsic transconductance and the source-access resistance, flat transconductance with high linearity is achieved experimentally. The laterally gated structure shows flat transconductance and small-signal power gain over a larger span of gate voltage that is 2.5 times higher than a planar device. Moreover, 6.9-dB improvement in output intercept point (OIP3)/P DC is achieved. This approach can be used to improve the linearity of AlGaN/GaN HEMTs at the device level.
Open Access
DC and RF performance of lateral AlGaN/GaN FinFET with ultrathin gate dielectric
(Institute of Physics Publishing Ltd., 2022-06-23) Yılmaz, Doğan; Odabaşı, O.; Salkım, Gurur; Urfalı, Emirhan; Akoğlu, Büşra Çankaya; Özbay, Ekmel; Altındal, Ş.
In this study, an enhancement-mode (E-mode) GaN high electron mobility transistor (HEMT) with lateral tri-gate structure field effect transistor (FinFET) is proposed. To passivate the fin width, while keeping the normally-off performance of the FinFET intact, an ultrathin aluminium-oxide/sapphire (Al2O3) gate dielectric is proposed (in a basic single-finger 0.125 mm device). Later, the DC and radio frequency (RF) performances of the proposed FinFET designs (with optimized fin width and Al2O3 thickness) are compared with that of conventional planar HEMT. DC and RF measurements are performed using power transistors in ten-fingers configuration, with a total gate periphery of 2.5 mm. The effect of Fin structure and Al2O3 thickness on the electrical performance of HEMTs, including threshold voltage (Vth) shift, transconductance (gm) linearity, small-signal gain, cut off frequency (f t), output power (Pout), and power-added efficiency (PAE) are investigated. Based on our findings, FinFET configuration imposes normally-off functionality with a Vth = 0.2 V, while the planar architecture has a Vth = −3.7 V. Originating from passivation property of the alumina layer, the FinFET design exhibits two orders of magnitude smaller drain and gate leakage currents compared to the planar case. Moreover, large signal RF measurements reveals an improved Pout density by over 50% compared to planar device, attributed to reduced thermal resistance in FinFETs stemming from additional lateral heat spreading of sidewall gates. Owing to its superior DC and RF performance, the proposed FinFET design with ultrathin gate dielectric could bear the potential of reliable operating for microwave power applications, by further scaling of the gate length.