Browsing by Subject "FinHEMT"

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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
Improved robustness, stability and linearity in GaN based high electron mobility transistors for 5G applications
(2021-06) Odabaşı, Oğuz
5G technology requires high frequency and high power transistors. GaN-based high-electron-mobility transistors (HEMTs) are promising candidates to answer these needs. Although it is studied nearly for 30 years, there are still problems with this technology such as high non-linearity, unstable behavior and uncertain-ties in lifetime estimations, to take the lead. Some of the most important problems of GaN HEMT technology are studied elaborately in this thesis. Electro-thermal simulations are used to analyze the heating behavior of HEMT power devices under operation and a new more re-alistic model is developed. Fabrication of devices is governed and highly linear transistors with 6.4 V gate voltage span are achieved by using ﬁn-like structures. 6.5 dB improvement in OIP3 is obtained compared to conventional devices. Fi-nally, the stability and robustness of these devices are studied in the view of passivation. Signiﬁcant improvement in surface morphology, DC operation, long-term stability, pulsed IV performance, and forward gate bias stress durability has been demonstrated. Findings will help the implementation of GaN HEMT devices into 5G applications.