Browsing by Subject "AlGaN/GaN HEMT"
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Item 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, EkmelThe 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.Item Embargo Nonalloyed ohmic contact development with n+InGaN regrowth method and analysis of its effect on AlGaN/GaN HEMT devices(Elsevier Ltd, 2023-03-22) Toprak, Ahmet; Özbay, EkmelIn this study, the DC performance of AlGaN/GaN based HEMT devices of different geometries (designed to operate in the S, X and Ka-band frequency ranges) with regrown degenerately doped n + In0.12GaN nonalloyed ohmic contacts on different epitaxial structures were investigated. Once the optimal recess etch depth and regrowth thickness for drain and source contacts were determined, the effects of alloyed and nonalloyed ohmic contacts on the maximum drain current (IDS,max), ON‐resistance (Ron), maximum DC transconductance (gm), pinch-off voltage (Vth), drain leakage current (ID,leak), and gate leakage current (IG,leak) were investigated for S, X and Ka-band HEMT devices. The results showed that the use of nonalloyed ohmic contacts resulted in decreasing Rc with a better surface morphology. Additionally, the nonalloyed ohmic contact structure with low contact resistance caused an increase in the IDS,max and gm values by reducing the Ron resistance, and also reducing the ID,leak and IG,leak leakage currents by preventing the surface distortions and trap formations due to the absence of high temperature. Although there was no dramatic change in Vth for S, X and Ka-band HEMT devices, Vth shifts towards positive in S and X-band devices, and towards negative in Ka-band devices.Item Open Access S-band GaN based low noise MMIC amplifier design and characterization(Bilkent University, 2019-02) Taşcı, MuhittinLow Noise Amplifiers (LNA) are widely preferred components in receiver frontend modules. The received signal level is generally very low and amplifying it without adding too much noise is very crucial in communication systems. In this thesis study design, fabrication and test of three Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) based Monolithic Microwave Circuit (MMIC) LNAs are presented. Inductive source feedback topology is used to obtain both better input return loss and noise figure. All three designs achieve higher than 20 dB gain, better than 10 dB input return loss and their noise figure values are 2 dB, 1.5 dB and 1 dB in S-band. High resistive gate biasing is utilized at third design to increase input power handling. Size reduction is very important in MMIC technology. The first design is 3 x 5 mm and the second design is 2 x 3.5 mm, % 46 size reduction is achieved. In GaN technology controlling SiN layer thickness is very problematic and this fabrication step affects capacitor values. The second and third LNA designs presented in this research, matching circuitries and implicitly overall characteristics are not in uenced too much by a change of capacitor values. Targeted bandwidth is 2.7-3.5 GHz, achieved frequency range is 1.5 GHz (from 2.5 GHz to 4 GHz). The three LNA designs have 28.1 dBm, 33.4 dBm, and 35.9 dBm output third-order intercept point respectively. Output powers at 1-dB compression points are 18.2 dBm, 23.4 dBm and 25.9 dBm. For all three LNA designs, group delay is less than 0.3 nanoseconds.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).Item Open Access Ultrathin interfacial layer and pre-gate annealing to suppress virtual gate formation in GaN-based transistors: The impact of trapping and fluorine inclusion(Institute of Electrical and Electronics Engineers, 2022-08-31) Odabaşı, Oğuz; Ghobadi, Amir; Ghobadi, Türkan Gamze Ulusoy; Özbay, EkmelIn AlGaN/GaN high electron mobility transistors (HEMTs), the long-term operation of the device is adversely affected by threshold voltage ( Vth ) instability and current collapse. In this letter, using structural and electrical analyses, the impact of trapping and fluorine (F) inclusion on the device operation is scrutinized. It is found that SiNx interfacial layer significantly reduced the formation of defects, during the ohmic annealing process. Moreover, the incorporation of F ions into GaN bulk, during the gate etch process, triggers the virtual gate phenomenon. This effect has also been mitigated via the pre-gate annealing (PGA) process. As a result of these modifications, a stable operation with minimized lag performance has been achieved.