Browsing by Subject "Vth shift"

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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.
Open Access
The effect of post-metal annealing on DC and RF performance of AlGaN/GaN HEMT
(Institute of Physics Publishing Ltd., 2022-12-15) Akoğlu, Büşra Çankaya; Yılmaz, Doğan; Salkım, Gurur; Özbay, Ekmel
The effects of gate post-metal annealing (PMA) on the DC and RF characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) were investigated. The unannealed and post gate-metal annealed AlGaN/GaN HEMTs were fully fabricated using NANOTAM's 0.5 μm gate length technology. PMA was performed at 450 °C for 10 min in nitrogen ambient for one of the wafers. The main focus was the effect of PMA on the electrical performance of HEMTs, including gate resistivity, transconductance, small-signal gain, output power (Pout), and threshold voltage (Vth) shift. It is achieved that HEMT with PMA has a gain of 18.5 dB, while HEMT without PMA shows a small-signal gain of 21.8 dB, as the PMA process increases the gate resistance (Rg) and decreases the transconductance (gm). The large-signal performance of the sample with PMA is better than the one without PMA, having an increase of 1.4 W/mm in Pout from 20.9 W to 24.4 W. The transistor with PMA also demonstrates a reliable gate performance and stable Vth, and the wafer exhibits better uniformity.