Browsing by Author "Şen, Ö."
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Item Open Access Effect of gate structures on the DC and RF performance of AlGaN/GaN HEMTs(Institute of Physics Publishing, 2018) Toprak, Ahmet; Osmanoǧlu, Sinan; Öztürk, Mustafa; Yılmaz, Doğan; Cengiz, Ö.; Şen, Ö.; Bütün, Bayram; Özcan, Ş.; Özbay, EkmelThis work analyzes the effect of various gate structures on the DC and radio frequency (RF) performance of AlGaN/GaN high-electron mobility transistors (HEMTs). AlGaN/GaN HEMT devices with a 3 μm drain-to-source spacing, 125 μm gate width and 0.3 μm gate length in various gate structures were fabricated to achieve the desired frequency response with a robust, high yield, and repeatable process. The maximum drain current (IDS,max), maximum DC transconductance (gm), pinch-off voltage (Vth), current-gain cutoff frequency (fT), maximum oscillation frequency (fmax), and RF characteristics of the devices in terms of the small-signal gain and RF output power (Pout) at 8 GHz were investigated. The results showed that the output power is increased by 1 dB when the gate structure is changed from field plate to gamma gate. The Vth, gm, fT and fmax values are maximized when the thickness of the passivation layer between the gate foot and the gate head is minimized. It is shown that the IDS,max is decreased and Pout is increased when the gate recess etching process is performed.Item Open Access An S-Band high gain AlGaN/GaN HEMT MMIC low noise amplifier(IEEE, 2019) Muhittin, Tasçı; Şen, Ö.; Özbay, EkmelIn this paper design, fabrication and measurement of a GaN HEMT based Monolithic Microwave Integrated Circuit (MMIC) Low Noise Amplifier (LNA) is presented. 12-Term equivalent circuit modeling is exacuted. Inductive source feedback topology is used to obtain low Noise Figure (NF) with appropriate input return loss. The gain of this design is higher than 25 dB, input return loss is better than 13 dB and NF value is 1.6 dB in S band. This work is only 3 x 5 mm. LNA has 28.1 dBm output third-order intercept point. Output power at 1-dB compression point is 18.2 dBm. Group delay is less than 0.3 nanoseconds. Due to superior properties of GaN technology, without NF performance degradation GaN LNA enables to high input power handling (P in is 20 dBm, CW, 10 mins).