Browsing by Author "Aras, Erdem"
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Item Unknown 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, EkmelIn 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.Item Unknown Design and robustness improvement of high-performance LNA using 0.15 μm GaN technology for X-band applications(John Wiley & Sons Ltd., 2022-07) Zafar, Salahuddin; Çankaya Akoğlu, Büşra; Aras, Erdem; Yılmaz, Doğan; Nawaz, Muhammad İmran; Kashif, Ahsanullah; Özbay, EkmelIn this paper, we present a highly robust GaN-based X-band low-noise amplifier (LNA) showing promising small-signal and noise performance as well as good linearity. The LNA is fabricated using in-house 0.15 μm AlGaN/GaN on a SiC HEMT process. Owing to the optimum choice of HEMT topologies and simultaneous matching technique, LNA achieves a noise figure better than 2 dB, output power at 1 dB gain compression higher than 19 dB, input and output reflection coefficients better than −9 and −11 dB, respectively. The small-signal gain of LNA is more than 19 dB for the whole band, and NF has a minimum of 1.74 dB at 10.2 GHz. LNA obtains an OIP3 up to 34.2 dBm and survives input power as high as 42 dBm. Survivability is investigated in terms of gain compression and forward gate current. Reverse recovery time (RRT), a crucial parameter for radar front-ends, is explored with respect to the RC time constant and trap phenomenon. The analysis shows that the significant contribution in RRT is due to traps while the RC time constant is in the nanoseconds range. Moreover, this study also addresses the requirement and choice of a DC gate feed resistor for the subsequent stages in a multi-stage design. The size of the designed LNA chip is 3 mm (Formula presented.) 1.2 mm only.Item Open Access Design of GaN-based X-band LNAs to achieve sub-1.2 dB noise figure(Wiley, 2022-08-21) Zafar, Salahuddin; Aras, Erdem; Cankaya Akoglu, Busra; Tendurus, Gizem; Nawaz, Muhammad Imran; Kashif, Ahsanullah; Ozbay, EkmelGaAs and SiGe technologies take an edge over GaN-based devices in terms of better noise figure (NF). In this article, we present HEMT topologies and design techniques to achieve a sub-1.2 dB NF for a GaN-based X-band low-noise amplifier (LNA). This NF is comparable with state-of-the-art reported works in competitive GaAs and SiGe technologies. Moreover, this is the best reported NF in X-band using GaN technology to date. Two LNAs are fabricated using in-house 0.15 μm AlGaN/GaN on the SiC HEMT process. LNA-1 has inductive source degenerated (ISD) HEMTs at both stages, while LNA-2 has ISD HEMT at the first and common source at the second stage. The significance of ISD HEMT, for the first or subsequent stages in a multi-stage design, towards NF improvement is addressed. The criticality of stability networks towards NF contribution and its design is discussed in detail. Furthermore, even-mode stability of each HEMT after complete LNA design is assured using the S-probe method in Pathwave Advanced Design Systems.