@article{probst_twiddy_hatada_pavlidis_daniele_sode_2024, title={Development of Direct Electron Transfer-Type Extended Gate Field Effect Transistor Enzymatic Sensors for Metabolite Detection}, volume={96}, ISSN={["1520-6882"]}, url={https://doi.org/10.1021/acs.analchem.3c04599}, DOI={10.1021/acs.analchem.3c04599}, abstractNote={In this work, direct electron transfer (DET)-type extended gate field effect transistor (EGFET) enzymatic sensors were developed by employing DET-type or quasi-DET-type enzymes to detect glucose or lactate in both 100 mM potassium phosphate buffer and artificial sweat. The system employed either a DET-type glucose dehydrogenase or a quasi-DET-type lactate oxidase, the latter of which was a mutant enzyme with suppressed oxidase activity and modified with amine-reactive phenazine ethosulfate. These enzymes were immobilized on the extended gate electrodes. Changes in the measured transistor drain current (ID) resulting from changes to the working electrode junction potential (φ) were observed as glucose and lactate concentrations were varied. Calibration curves were generated for both absolute measured ID and ΔID (normalized to a blank solution containing no substrate) to account for variations in enzyme immobilization and conjugation to the mediator and variations in reference electrode potential. This work resulted in a limit of detection of 53.9 μM (based on ID) for glucose and 2.12 mM (based on ID) for lactate, respectively. The DET-type and Quasi-DET-type EGFET enzymatic sensor was then modeled using the case of the lactate sensor as an equivalent circuit to validate the principle of sensor operation being driven through OCP changes caused by the substrate-enzyme interaction. The model showed slight deviation from collected empirical data with 7.3% error for the slope and 8.6% error for the y-intercept.}, number={10}, journal={ANALYTICAL CHEMISTRY}, author={Probst, David and Twiddy, Jack and Hatada, Mika and Pavlidis, Spyridon and Daniele, Michael and Sode, Koji}, year={2024}, month={Feb}, pages={4076–4085} }
 @article{hatada_pavlidis_sode_2024, title={Development of a glycated albumin sensor employing dual aptamer-based extended gate field effect transistors}, volume={251}, ISSN={["1873-4235"]}, url={https://doi.org/10.1016/j.bios.2024.116118}, DOI={10.1016/j.bios.2024.116118}, abstractNote={Glycated albumin (GA), defined as the percentage of serum albumin glycation, is a mid-term glycemic control marker for diabetes. The concentrations of both glycated human serum albumin (GHSA) and total human serum albumin (HSA) are required to calculate GA. Here, we report the development of a GA sensor employing two albumin aptamers: anti-GHSA aptamer which is specific to GHSA and anti-HSA aptamer which recognizes both glycated and non-glycated HSA. We combine these aptamers with extended gate field effect transistors (EGFETs) to realize GA monitoring without the need to pretreat serum samples, and therefore suitable for point of care and home-testing applications. Using anti-GHSA aptamer-immobilized electrodes and EGFETs, we measured GHSA concentrations between 0.110 μM within 20 min. The sensor was able to measure GHSA concentration in the presence of BSA for a range of known GA levels (5–29%). With anti-HSA aptamer-immobilized electrodes and EGFETs, we measured total HSA concentrations from 117 μM. Furthermore, GHSA and total HSA concentrations of both healthy and diabetic-level samples were determined with GHSA and HSA sensors. The measured GHSA and total HSA concentrations in three samples were used to determine respective GA percentages, and our calculations agreed with GA levels determined by reference methods. Thus, we developed simple and rapid dual aptamer-based EGFET sensors to monitor GA through measuring GHSA and total HSA concentration, without the need for sample pretreatment, a mandatory step in the current standard of enzymatic GA monitoring.}, journal={BIOSENSORS & BIOELECTRONICS}, author={Hatada, Mika and Pavlidis, Spyridon and Sode, Koji}, year={2024}, month={May} }
 @article{richardson_kline_pavlidis_2024, title={Performance of an aptamer-based neuropeptide Y potentiometric sensor: dependence on spacer molecule selection}, ISSN={["1521-4109"]}, DOI={10.1002/elan.202300387}, abstractNote={na}, journal={ELECTROANALYSIS}, author={Richardson, Hayley and Kline, Alex and Pavlidis, Spyridon}, year={2024}, month={Jul} }
 @article{stein_khachariya_mecouch_mita_reddy_tweedie_sierakowski_kamler_bockowski_kohn_et al._2023, title={Analysis of Vertical GaN JBS and p-n Diodes by Mg Ion Implantation and Ultrahigh-Pressure Annealing}, volume={12}, ISSN={["1557-9646"]}, url={https://doi.org/10.1109/TED.2023.3339592}, DOI={10.1109/TED.2023.3339592}, abstractNote={We report on vertical GaN junction barrier Schottky (JBS) diodes formed by Mg ion implantation and ultrahigh -pressure annealing (UHPA). The static ON-state characteristics of the diodes show an ideality factor of 1.05, a turn-on voltage of ~0.7 V, a current rectification ratio of $\sim 10^{11}$ , and a low differential specific ON-resistance that scales with Schottky stripe width in fair agreement with the analytical model. The reverse leakage dependence on Schottky stripe width also agrees well with the analytical model. Implanted p-n junction diodes fabricated on the same wafer exhibit avalanche breakdown in reverse bias with a positive temperature coefficient, but the forward current is limited by a series barrier. Temperature-dependent current–voltage measurements of th p-n diodes verify the presence of the implanted p-n junction and reveal an additional 0.43-eV barrier, which we hypothesize arises from a p-Schottky contact and forms a second diode back-to-back with the p-n junction. This interpretation is supported by analysis of the capacitance–voltage characteristics of the implanted p-n diodes, epitaxial p-n diodes fabricated with intentional p-Schottky contacts, and comparison to TCAD simulations. Ultimately, the presence of the p-Schottky contact does not hinder JBS diode operation. The use of diffusion-aware designs and/or diffusion reduction represents future directions for Mg implantation technology in GaN power devices.}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Stein, Shane R. and Khachariya, Dolar and Mecouch, Will and Mita, Seiji and Reddy, Pramod and Tweedie, James and Sierakowski, Kacper and Kamler, Grzegorz and Bockowski, Michal and Kohn, Erhard and et al.}, year={2023}, month={Dec} }
 @article{sengupta_vaidya_szymanski_khachariya_bockowski_kamler_reddy_sitar_collazo_pavlidis_2023, title={Chemical Vapor Deposition of Monolayer MoS2 on Chemomechanically Polished N-Polar GaN for Future 2D/3D Heterojunction Optoelectronics}, volume={3}, ISSN={["2574-0970"]}, url={https://doi.org/10.1021/acsanm.3c00038}, DOI={10.1021/acsanm.3c00038}, abstractNote={The growth of monolayer MoS2 crystals on chemomechanically polished (CMP) N-polar GaN using PTAS-assisted chemical vapor deposition is demonstrated. The formation of monolayer MoS2 was initially prevented by the as-grown GaN’s large surface roughness. CMP reduces the roughness to 250 pm, enabling monolayer MoS2 triangles with edge lengths of 30 μm, a Raman peak separation of <20 cm–1, and an optical bandgap of 1.81 eV, which is on par with those obtained on smooth Ga-polar GaN. It is thus demonstrated that high-quality MoS2 monolayers can be obtained on N-polar GaN for future high-speed optoelectronic and quantum sensing applications.}, journal={ACS APPLIED NANO MATERIALS}, author={Sengupta, Rohan and Vaidya, Shipra and Szymanski, Dennis and Khachariya, Dolar and Bockowski, Michal and Kamler, Grzegorz and Reddy, Pramod and Sitar, Zlatko and Collazo, Ramon and Pavlidis, Spyridon}, year={2023}, month={Mar} }
 @article{quinones_khachariya_bagheri_reddy_mita_kirste_rathkanthiwar_tweedie_pavlidis_kohn_et al._2023, title={Demonstration of near-ideal Schottky contacts to Si-doped AlN}, volume={123}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0174524}, DOI={10.1063/5.0174524}, abstractNote={Near-ideal behavior in Schottky contacts to Si-doped AlN was observed as evidenced by a low ideality factor of 1.5 at room temperature. A temperature-independent Schottky barrier height of 1.9 eV was extracted from temperature-dependent I–V measurements. An activation energy of ∼300 meV was observed in the series resistance, which corresponded to the ionization energy of the deep Si donor state. Both Ohmic and Schottky contacts were stable up to 650 °C, with around four orders of magnitude rectification at this elevated temperature. These results demonstrate the potential of AlN as a platform for power devices capable of operating in extreme environments.}, number={17}, journal={APPLIED PHYSICS LETTERS}, author={Quinones, C. E. and Khachariya, D. and Bagheri, P. and Reddy, P. and Mita, S. and Kirste, R. and Rathkanthiwar, S. and Tweedie, J. and Pavlidis, S. and Kohn, E. and et al.}, year={2023}, month={Oct} }
 @article{palmese_xue_pavlidis_wierer_2023, title={Enhancement-Mode AlInN/GaN High-Electron-Mobility Transistors Enabled by Thermally Oxidized Gates}, volume={12}, ISSN={["1557-9646"]}, url={https://doi.org/10.1109/TED.2023.3343313}, DOI={10.1109/TED.2023.3343313}, abstractNote={Enhancement mode AlInN/gallium nitride (GaN) high-electron-mobility transistors (HEMTs) are fabricated by thermally oxidizing the barrier region under the gate. The oxidation is performed at 850 °C in <inline-formula> <tex-math notation="LaTeX">$\text{O}_{{2}}$ </tex-math></inline-formula>, and a SiNx mask is used to achieve selective oxidization of the AlInN layer. For comparison, a standard Schottky gate and atomic layer deposition (ALD) Al2O3 metal–insulator–semiconductor (MIS) HEMTs are fabricated from the same structure and show depletion mode behavior as expected. Scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) mappings are performed to characterize the gate of the oxidized HEMTs, showing complete oxidation of the AlInN barrier. All the devices are tested to determine their transfer and output characteristics. The results show that the thermally oxidized gate produces a positive shift in threshold voltage at ~4 V and low currents (<inline-formula> <tex-math notation="LaTeX">$\sim 2\times 10^{-{7}}$ </tex-math></inline-formula> mA/mm) at zero gate voltage. The oxidized HEMTs are also subjected to postmetallization annealing (PMA) at 400 °C and 500 °C for 10 min flowing 1000 sccm of <inline-formula> <tex-math notation="LaTeX">$\text{N}_{{2}}$ </tex-math></inline-formula>, retaining enhancement mode behavior and leading to a further positive shift in threshold voltage.}, journal={IEEE TRANSACTIONS ON ELECTRON DEVICES}, author={Palmese, Elia and Xue, Haotian and Pavlidis, Spyridon and Wierer, Jonathan J.}, year={2023}, month={Dec} }
 @article{pavlidis_2023, title={Looking for Some Fun in the Sun? Be a Student Volunteer!}, volume={24}, ISSN={["1557-9581"]}, DOI={10.1109/MMM.2023.3242920}, abstractNote={Lists future events that should be of interest to practitioners and researchers.}, number={5}, journal={IEEE MICROWAVE MAGAZINE}, author={Pavlidis, Spyridon Spyros}, year={2023}, month={May}, pages={142–143} }
 @article{stein_khachariya_mita_breckenridge_tweedie_reddy_sierakowski_kamler_bockowski_kohn_et al._2023, title={Schottky contacts on ultra-high-pressure-annealed GaN with high rectification ratio and near-unity ideality factor}, volume={16}, ISSN={["1882-0786"]}, DOI={10.35848/1882-0786/acc443}, abstractNote={Abstract}, number={3}, journal={APPLIED PHYSICS EXPRESS}, author={Stein, Shane R. and Khachariya, Dolar and Mita, Seiji and Breckenridge, M. Hayden and Tweedie, James and Reddy, Pramod and Sierakowski, Kacper and Kamler, Grzegorz and Bockowski, Michal and Kohn, Erhard and et al.}, year={2023}, month={Mar} }
 @article{stein_khachariya_pavlidis_2022, title={Design and performance analysis of GaN vertical JFETs with ion-implanted gates}, volume={37}, ISSN={["1361-6641"]}, DOI={10.1088/1361-6641/ac9d00}, abstractNote={Abstract}, number={12}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Stein, Shane R. and Khachariya, Dolar and Pavlidis, Spyridon}, year={2022}, month={Dec} }
 @article{szymanski_khachariya_eldred_bagheri_washiyama_chang_pavlidis_kirste_reddy_kohn_et al._2022, title={GaN lateral polar junction arrays with 3D control of doping by supersaturation modulated growth: A path toward III-nitride superjunctions}, volume={131}, ISSN={["1089-7550"]}, url={https://doi.org/10.1063/5.0076044}, DOI={10.1063/5.0076044}, abstractNote={We demonstrate a pathway employing crystal polarity controlled asymmetric impurity incorporation in the wide bandgap nitride material system to enable 3D doping control during the crystal growth process. The pathway involves polarity specific supersaturation modulated growth of lateral polar structures of alternating Ga- and N-polar GaN domains. A STEM technique of integrated differential phase contrast is used to image the atomic structure of the different polar domains and their single atomic plane boundaries. As a demonstration, 1 μm wide alternating Ga- and N-polar GaN domains exhibiting charge balanced and periodic domains for superjunction technology were grown. The challenges in characterizing the resulting 3D doping profile were addressed with atom probe tomography with atomic scale compositional resolution corroborating capacitance measurements and secondary-ion mass spectroscopy analysis.}, number={1}, journal={JOURNAL OF APPLIED PHYSICS}, author={Szymanski, Dennis and Khachariya, Dolar and Eldred, Tim B. and Bagheri, Pegah and Washiyama, Shun and Chang, Alexander and Pavlidis, Spyridon and Kirste, Ronny and Reddy, Pramod and Kohn, Erhard and et al.}, year={2022}, month={Jan} }
 @article{reddy_mecouch_breckenridge_khachariya_bagheri_kim_guan_mita_moody_tweedie_et al._2022, title={Large-Area, Solar-Blind, Sub-250 nm Detection AlGaN Avalanche Photodiodes Grown on AlN Substrates}, volume={3}, ISSN={["1862-6270"]}, url={https://doi.org/10.1002/pssr.202100619}, DOI={10.1002/pssr.202100619}, abstractNote={Herein, Al‐rich AlGaN‐based avalanche photodiodes (APDs) grown on single crystal AlN substrates high ultraviolet‐C sensitivity for λ < 200 nm are fabricated, while exhibiting blindness to λ > 250 nm. A maximum quantum efficiency of 68% and peak gain of 320 000 are estimated resulting in a figure of merit of ≈220 000 in devices with ϕ = 100 μm. As expected, a decrease in gain with increase in device size is observed and a gain of ≈20 000 is estimated in devices with ϕ = 400 μm. Overall, two orders of magnitude higher performance are observed in APDs on single crystal AlN substrates compared to those on sapphire.}, journal={PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS}, publisher={Wiley}, author={Reddy, Pramod and Mecouch, Will and Breckenridge, M. Hayden and Khachariya, Dolar and Bagheri, Pegah and Kim, Ji Hyun and Guan, Yan and Mita, Seiji and Moody, Baxter and Tweedie, James and et al.}, year={2022}, month={Mar} }
 @article{rathkanthiwar_szymanski_khachariya_bagheri_kim_mita_reddy_kohn_pavlidis_kirste_et al._2022, title={Low resistivity, p-type, N-Polar GaN achieved by chemical potential control}, volume={15}, ISSN={["1882-0786"]}, DOI={10.35848/1882-0786/ac8273}, abstractNote={Abstract}, number={8}, journal={APPLIED PHYSICS EXPRESS}, author={Rathkanthiwar, Shashwat and Szymanski, Dennis and Khachariya, Dolar and Bagheri, Pegah and Kim, Ji Hyun and Mita, Seiji and Reddy, Pramod and Kohn, Erhard and Pavlidis, Spyridon and Kirste, Ronny and et al.}, year={2022}, month={Aug} }
 @article{sengupta_dangi_krylyuk_davydov_pavlidis_2022, title={Phase transition of Al2O3-encapsulated MoTe2 via rapid thermal annealing}, volume={121}, ISSN={["1077-3118"]}, DOI={10.1063/5.0097844}, abstractNote={Among group VI transition metal dichalcogenides, MoTe2 is predicted to have the smallest energy offset between semiconducting 2H and semimetallic 1T′ states. This makes it an attractive phase change material for both electronic and optoelectronic applications. Here, we report fast, nondestructive, and full phase change in Al2O3-encapsulated 2H-MoTe2 thin films to 1T′-MoTe2 using rapid thermal annealing at 900 °C. Phase change was confirmed using Raman spectroscopy after a short annealing duration of 10 s in both vacuum and nitrogen ambient. No thickness dependence of the transition temperatures was observed for flake thickness ranging from 1.5 to 8 nm. These results represent a major step forward in understanding the structural phase transition properties of MoTe2 thin films using external heating and underline the importance of surface encapsulation for avoiding thin film degradation.}, number={3}, journal={APPLIED PHYSICS LETTERS}, author={Sengupta, Rohan and Dangi, Saroj and Krylyuk, Sergiy and Davydov, Albert V. and Pavlidis, Spyridon}, year={2022}, month={Jul} }
 @article{rathkanthiwar_bagheri_khachariya_mita_pavlidis_reddy_kirste_tweedie_sitar_collazo_2022, title={Point-defect management in homoepitaxially grown Si-doped GaN by MOCVD for vertical power devices}, volume={15}, ISSN={["1882-0786"]}, DOI={10.35848/1882-0786/ac6566}, abstractNote={Abstract}, number={5}, journal={APPLIED PHYSICS EXPRESS}, author={Rathkanthiwar, Shashwat and Bagheri, Pegah and Khachariya, Dolar and Mita, Seiji and Pavlidis, Spyridon and Reddy, Pramod and Kirste, Ronny and Tweedie, James and Sitar, Zlatko and Collazo, Ramon}, year={2022}, month={May} }
 @article{khachariya_mita_reddy_dangi_dycus_bagheri_breckenridge_sengupta_rathkanthiwar_kirste_et al._2022, title={Record >10 MV/cm mesa breakdown fields in Al0.85Ga0.15N/Al0.6Ga0.4N high electron mobility transistors on native AlN substrates}, volume={120}, ISSN={["1077-3118"]}, DOI={10.1063/5.0083966}, abstractNote={The ultra-wide bandgap of Al-rich AlGaN is expected to support a significantly larger breakdown field compared to GaN, but the reported performance thus far has been limited by the use of foreign substrates. In this Letter, the material and electrical properties of Al0.85Ga0.15N/Al0.6Ga0.4N high electron mobility transistors (HEMT) grown on a 2-in. single crystal AlN substrate are investigated, and it is demonstrated that native AlN substrates unlock the potential for Al-rich AlGaN to sustain large fields in such devices. We further study how Ohmic contacts made directly to a Si-doped channel layer reduce the knee voltage and increase the output current density. High-quality AlGaN growth is confirmed via scanning transmission electron microscopy, which also reveals the absence of metal penetration at the Ohmic contact interface and is in contrast to established GaN HEMT technology. Two-terminal mesa breakdown characteristics with 1.3 μm separation possess a record-high breakdown field strength of ∼11.5 MV/cm for an undoped Al0.6Ga0.4N-channel layer. The breakdown voltages for three-terminal devices measured with gate-drain distances of 4 and 9 μm are 850 and 1500 V, respectively.}, number={17}, journal={APPLIED PHYSICS LETTERS}, author={Khachariya, Dolar and Mita, Seiji and Reddy, Pramod and Dangi, Saroj and Dycus, J. Houston and Bagheri, Pegah and Breckenridge, M. Hayden and Sengupta, Rohan and Rathkanthiwar, Shashwat and Kirste, Ronny and et al.}, year={2022}, month={Apr} }
 @article{khachariya_stein_mecouch_breckenridge_rathkanthiwar_mita_moody_reddy_tweedie_kirste_et al._2022, title={Vertical GaN junction barrier Schottky diodes with near-ideal performance using Mg implantation activated by ultra-high-pressure annealing}, volume={15}, ISSN={["1882-0786"]}, DOI={10.35848/1882-0786/ac8f81}, abstractNote={Abstract}, number={10}, journal={APPLIED PHYSICS EXPRESS}, author={Khachariya, Dolar and Stein, Shane and Mecouch, Will and Breckenridge, M. Hayden and Rathkanthiwar, Shashwat and Mita, Seiji and Moody, Baxter and Reddy, Pramod and Tweedie, James and Kirste, Ronny and et al.}, year={2022}, month={Oct} }
 @article{breckenridge_bagheri_guo_sarkar_khachariya_pavlidis_tweedie_kirste_mita_reddy_et al._2021, title={High n-type conductivity and carrier concentration in Si-implanted homoepitaxial AlN}, volume={118}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0042857}, DOI={10.1063/5.0042857}, abstractNote={We demonstrate Si-implanted AlN with high conductivity (>1 Ω−1 cm−1) and high carrier concentration (5 × 1018 cm−3). This was enabled by Si implantation into AlN with a low threading dislocation density (TDD) (<103 cm−2), a non-equilibrium damage recovery and dopant activation annealing process, and in situ suppression of self-compensation during the annealing. Low TDD and active suppression of VAl-nSiAl complexes via defect quasi Fermi level control enabled low compensation, while low-temperature, non-equilibrium annealing maintained the desired shallow donor state with an ionization energy of ∼70 meV. The realized n-type conductivity and carrier concentration are over one order of magnitude higher than that reported thus far and present a major technological breakthrough in doping of AlN.}, number={11}, journal={APPLIED PHYSICS LETTERS}, author={Breckenridge, M. Hayden and Bagheri, Pegah and Guo, Qiang and Sarkar, Biplab and Khachariya, Dolar and Pavlidis, Spyridon and Tweedie, James and Kirste, Ronny and Mita, Seiji and Reddy, Pramod and et al.}, year={2021}, month={Mar} }
 @article{bagheri_reddy_mita_szymanski_kim_guan_khachariya_klump_pavlidis_kirste_et al._2021, title={On the Ge shallow-to-deep level transition in Al-rich AlGaN}, volume={130}, ISSN={["1089-7550"]}, url={https://doi.org/10.1063/5.0059037}, DOI={10.1063/5.0059037}, abstractNote={Contrary to the arsenides where donors undergo stable DX transition, we find that Ge in AlGaN does not suffer from the DX transition; instead, it undergoes a shallow donor (30 meV) to deep donor (150 meV) transition at ∼50% Al content in the alloy. This finding is of profound technological importance as it removes fundamental doping limitations in AlGaN and AlN imposed by the presumed DX−1 acceptor state. The charge state of Ge below and above the transition was determined by co-doping with Si, which remains a shallow donor in AlGaN for up to 80% Al. It was found that Ge occupied a donor state with a (0/+) thermodynamic transition for AlGaN alloys below and above the transition. Ge as a shallow donor was completely ionized at room temperature; however, the ionization of the deep donor required elevated temperatures, commensurate with its higher ionization energy. This behavior is not unique to Ge; preliminary findings show that Si and O in AlGaN may behave similarly.}, number={5}, journal={JOURNAL OF APPLIED PHYSICS}, author={Bagheri, Pegah and Reddy, Pramod and Mita, Seiji and Szymanski, Dennis and Kim, Ji Hyun and Guan, Yan and Khachariya, Dolar and Klump, Andrew and Pavlidis, Spyridon and Kirste, Ronny and et al.}, year={2021}, month={Aug} }
 @article{khachariya_szymanski_breckenridge_reddy_kohn_sitar_collazo_pavlidis_2021, title={On the characteristics of N-polar GaN Schottky barrier contacts with LPCVD SiN interlayers}, volume={118}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0039888}, DOI={10.1063/5.0039888}, abstractNote={We study the behavior of N-polar GaN Schottky diodes with low-pressure chemical vapor deposited (LPCVD) SiN interlayers and unveil the important role of an amphoteric miniband formed in this interlayer due to a previously identified and dominating Si dangling bond defect. Through analysis of temperature-dependent current–voltage (I–V–T), capacitance–voltage (C–V), and x-ray photoelectron spectroscopy measurements, we observe that when nickel is deposited on LPCVD SiN pretreated with hydrofluoric acid, the SiN/GaN interface is responsible for determining the overall system's barrier height. By contrast, contact formation on oxidized LPCVD SiN leads to a metal/SiN-dominant barrier. We, consequently, propose band diagrams that account for an amphoteric miniband in LPCVD SiN, leading to a new understanding of LPCVD SiN as a lossy dielectric with surface barrier-dependent behavior.}, number={12}, journal={APPLIED PHYSICS LETTERS}, author={Khachariya, Dolar and Szymanski, Dennis and Breckenridge, M. Hayden and Reddy, Pramod and Kohn, Erhard and Sitar, Zlatko and Collazo, Ramon and Pavlidis, Spyridon}, year={2021}, month={Mar} }
 @article{reddy_khachariya_mecouch_breckenridge_bagheri_guan_kim_pavlidis_kirste_mita_et al._2021, title={Study on avalanche breakdown and Poole-Frenkel emission in Al-rich AlGaN grown on single crystal AlN}, volume={119}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/5.0062831}, DOI={10.1063/5.0062831}, abstractNote={We demonstrate that theoretical breakdown fields can be realized in practically dislocation free Al-rich AlGaN p-n junctions grown on AlN single crystal substrates. Furthermore, we also demonstrate a leakage current density in AlGaN that is independent of the device area, indicating a bulk leakage phenomenon and not surface or mesa-edge related. Accordingly, we identified the Poole–Frenkel emission from two types of point-defect traps in AlGaN as the primary source of reverse leakage before breakdown. Mg-doped AlGaN exhibited leakage currents due to a shallow trap at ∼0.16 eV in contrast with leakage currents observed in Si-doped AlGaN due to a deep trap at ∼1.8 eV.}, number={18}, journal={APPLIED PHYSICS LETTERS}, author={Reddy, Pramod and Khachariya, Dolar and Mecouch, Will and Breckenridge, M. Hayden and Bagheri, Pegah and Guan, Yan and Kim, Ji Hyun and Pavlidis, Spyridon and Kirste, Ronny and Mita, Seiji and et al.}, year={2021}, month={Nov} }
 @article{richardson_maddocks_peterson_daniele_pavlidis_2021, title={Toward Subcutaneous Electrochemical Aptasensors for Neuropeptide Y}, ISSN={["1930-0395"]}, DOI={10.1109/SENSORS47087.2021.9639832}, abstractNote={Subcutaneous sensors, similar to the continuous glucose monitor, are advantageous for identifying healthy and pathological patterns of circulating biomarkers. A biosensor for the detection of neuropeptide Y (NPY), a marker of stress, has been designed and tested for operation in a flexible microneedle form factor. The biosensing principle used is affinity binding of NPY to a DNA aptamer-functionalized electrode. A gold microelectrode was functionalized by formation of a self- assembled monolayer (SAM) of a thiol-modified NPY-binding aptamer and poly(ethylene glycol) methyl ether thiol (PEG). The sensors were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy, resulting in a response to NPY over 400 pM to 200 nM when tested in KCl and K3[Fe(CN)6]/K4[Fe(CN)6], and PBS.}, journal={2021 IEEE SENSORS}, author={Richardson, Hayley and Maddocks, Grace and Peterson, Kaila and Daniele, Michael and Pavlidis, Spyridon}, year={2021} }
 @article{stein_robbins_reddy_collazo_pavlidis_2021, title={UV illumination effects on AlGaN/GaN HEMTs for tunable RF oscillators}, ISSN={["2164-2958"]}, DOI={10.1109/RWS50353.2021.9360392}, abstractNote={We present the first investigation of AlGaN/GaN HEMTs as optically-controlled microwave semiconductor devices for use in next-generation, high-power microwave photonics systems. Measurements show a modest change in S21 in the presence of UV illumination that induces internal photoconductive and photovoltaic effects. This contrasts with the significant shift in the measured gate capacitance, which can be used to tune future oscillators. This is investigated through the design of a 2.4 GHz Pierce oscillator with an optical tuning range of 3 MHz.}, journal={2021 IEEE RADIO AND WIRELESS SYMPOSIUM (RWS)}, author={Stein, Shane and Robbins, Max and Reddy, Pramod and Collazo, Ramon and Pavlidis, Spyridon}, year={2021}, pages={168–170} }
 @article{cho_song_pavlidis_fleetwood_buchner_mcmorrow_paki_cressler_2018, title={An Electrostatic Discharge Protection Circuit Technique for the Mitigation of Single-Event Transients in SiGe BiCMOS Technology}, volume={65}, ISSN={0018-9499 1558-1578}, url={http://dx.doi.org/10.1109/tns.2017.2778946}, DOI={10.1109/tns.2017.2778946}, abstractNote={The impact of electrostatic discharge (ESD) protection circuits on the single-event transients (SETs) of RF building blocks in a 130-nm SiGe BiCMOS (8HP) platform is investigated. For proof-of-concept that SET mitigation can be accomplished through the use of an ESD protection circuit, a single-pole single-throw (SPST) switch was implemented using triple-well nFETs. For substrate noise coupling suppression, a P<sup>+</sup>, P<sup>−</sup> substrate (Psub) and N-well guard ring structures were applied. According to two-photon absorption laser experiment results, the SPST switch with ESD protection exhibits the smallest transient peaks at the RF input/output and <inline-formula> <tex-math notation="LaTeX">$\text{V}_{\mathrm {\mathbf {DD}}}$ </tex-math></inline-formula> ESD terminals. Based on these results, an SET mitigation strategy is proposed while maintaining the optimal circuit performance.}, number={1}, journal={IEEE Transactions on Nuclear Science}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Cho, Moon-Kyu and Song, Ickhyun and Pavlidis, Spyridon and Fleetwood, Zachary E. and Buchner, Stephen P. and McMorrow, Dale and Paki, Pauline and Cressler, John D.}, year={2018}, month={Jan}, pages={426–431} }
 @article{pavlidis_2018, title={RWW 2019-Five Colocated Conferences, Five Special Features}, volume={19}, ISSN={["1557-9581"]}, DOI={10.1109/MMM.2018.2862598}, abstractNote={Wireless technologies form a fundamental pillar of modern-day life, making it possible for us to easily and rapidly interact with individuals and businesses locally as well as halfway around the world. The world is data hungry. But it is not just humans contributing to this demand. With the advent of the Internet of Things (IoT), Internet of Space, and 5G technologies, what were once passive, inanimate objects are now participating in the conversation. Moreover, progress is being made on all levels, ranging from the emergence of competing semiconductor technologies to innovations in front-end topologies and systems. It is an exciting time to be a microwave engineer!}, number={7}, journal={IEEE MICROWAVE MAGAZINE}, author={Pavlidis, Spyridon}, year={2018}, pages={29-+} }
 @article{song_cho_fleetwood_gong_pavlidis_buchner_mcmorrow_paki_kaynak_cressler_2018, title={p-n-p-Based RF Switches for the Mitigation of Single-Event Transients in a Complementary SiGe BiCMOS Platform}, volume={65}, ISSN={0018-9499 1558-1578}, url={http://dx.doi.org/10.1109/tns.2017.2780120}, DOI={10.1109/tns.2017.2780120}, abstractNote={The benefits of using p-n-p silicon–germanium (SiGe) heterojuction bipolar transistors (HBTs) in radio frequency (RF) circuits for the mitigation of single-event transients (SETs) have been investigated. As a representative circuit example, p-n-p SiGe-HBT RF single-pole single-throw (SPST) switches have been designed in a complementary SiGe BiCMOS platform. The fabricated p-n-p-based RF switches provide comparable RF performance to n-p-n-based switches. In terms of SET transient peaks and duration, the p-n-p SiGe HBT RF switches exhibit a significant reduction in SET sensitivity compared with their n-p-n counterparts. In the frequency domain, the p-n-p switches show fewer low-frequency spurs than that of the n-p-n switches. In addition, inverse-mode p-n-p SiGe HBT switches provide the best overall SET response among all RF SPST switches investigated.}, number={1}, journal={IEEE Transactions on Nuclear Science}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Song, Ickhyun and Cho, Moon-Kyu and Fleetwood, Zachary E. and Gong, Yunyi and Pavlidis, Spyridon and Buchner, Stephen P. and McMorrow, Dale and Paki, Pauline and Kaynak, Mehmet and Cressler, John. D.}, year={2018}, month={Jan}, pages={391–398} }
 @article{pavlidis_bayraktaroglu_leedy_henderson_vogel_brand_2017, title={ALD TiO x  as a top-gate dielectric and passivation layer for InGaZnO115 ISFETs}, volume={32}, ISSN={0268-1242 1361-6641}, url={http://dx.doi.org/10.1088/1361-6641/aa8b33}, DOI={10.1088/1361-6641/aa8b33}, abstractNote={The suitability of atomic layer deposited (ALD) titanium oxide (TiOx) as a top gate dielectric and passivation layer for indium gallium zinc oxide (InGaZnO115) ion sensitive field effect transistors (ISFETs) is investigated. TiOx is an attractive barrier material, but reports of its use for InGaZnO thin film transistor (TFT) passivation have been conflicting thus far. In this work, it is found that the passivated TFT’s behavior depends on the TiOx deposition temperature, affecting critical device characteristics such as threshold voltage, field-effect mobility and sub-threshold swing. An O2 annealing step is required to recover TFT performance post passivation. It is also observed that the positive bias stress response of the passivated TFTs improves compared the original bare device. Secondary ion mass spectroscopy excludes the effects of hydrogen doping and inter-diffusion as sources of the temperature-dependent performance change, therefore indicating that oxygen gettering induced by TiOx passivation is the likely source of oxygen vacancies and, consequently, carriers in the InGaZnO film. It is also shown that potentiometric sensing using ALD TiOx exhibits a near Nernstian response to pH change, as well as minimizes VTH drift in TiOx passivated InGaZnO TFTs immersed in an acidic liquid. These results add to the understanding of InGaZnO passivation effects and underscore the potential for low-temperature fabricated InGaZnO ISFETs to be used as high-performance mobile chemical sensors.}, number={11}, journal={Semiconductor Science and Technology}, publisher={IOP Publishing}, author={Pavlidis, S and Bayraktaroglu, B and Leedy, K and Henderson, W and Vogel, E and Brand, O}, year={2017}, month={Oct}, pages={114004} }
 @article{pavlidis_pavlidis_heller_moore_vetury_graham_2017, title={Characterization of AlGaN/GaN HEMTs Using Gate Resistance Thermometry}, volume={64}, ISSN={0018-9383 1557-9646}, url={http://dx.doi.org/10.1109/ted.2016.2625264}, DOI={10.1109/ted.2016.2625264}, abstractNote={In this paper, gate resistance thermometry (GRT) was used to determine the channel temperature of AlGaN/GaN high electron-mobility transistors. Raman thermometry has been used to verify GRT by comparing the channel temperatures measured by both techniques under various bias conditions. To further validate this technique, a thermal finite-element model has been developed to model the heat dissipation throughout the devices. Comparisons show that the GRT method averages the temperature over the gate width, yielding a slightly lower peak temperature than Raman thermography. Overall, this method provides a fast and simple technique to determine the average temperature under both steady-state and pulsed bias conditions.}, number={1}, journal={IEEE Transactions on Electron Devices}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Pavlidis, Georges and Pavlidis, Spyridon and Heller, Eric R. and Moore, Elizabeth A. and Vetury, Ramakrishna and Graham, Samuel}, year={2017}, month={Jan}, pages={78–83} }
 @article{tsai_creedon_brightbill_pavlidis_brown_gray_shields_sayers_mooney_o'riordan_et al._2017, title={Direct correlation between potentiometric and impedance biosensing of           antibody-antigen interactions using an integrated system}, volume={111}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4986190}, DOI={10.1063/1.4986190}, abstractNote={A fully integrated system that combines extended gate field-effect transistor (EGFET)-based potentiometric biosensors and electrochemical impedance spectroscopy (EIS)-based biosensors has been demonstrated. This integrated configuration enables the sequential measurement of the same immunological binding event on the same sensing surface and consequently sheds light on the fundamental origins of sensing signals produced by FET and EIS biosensors, as well as the correlation between the two. Detection of both the bovine serum albumin (BSA)/anti-BSA model system in buffer solution and bovine parainfluenza antibodies in complex blood plasma samples was demonstrated using the integrated biosensors. Comparison of the EGFET and EIS sensor responses reveals similar dynamic ranges, while equivalent circuit modeling of the EIS response shows that the commonly reported total impedance change (ΔZtotal) is dominated by the change in charge transfer resistance (Rct) rather than surface capacitance (Csurface). Using electrochemical kinetics and the Butler-Volmer equation, we unveil that the surface potential and charge transfer resistance, measured by potentiometric and impedance biosensors, respectively, are, in fact, intrinsically linked. This observation suggests that there is no significant gain in using the FET/EIS integrated system and leads to the demonstration that low-cost EGFET biosensors are sufficient as a detection tool to resolve the charge information of biomolecules for practical sensing applications.}, number={7}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Tsai, Meng-Yen and Creedon, Niamh and Brightbill, Eleanor and Pavlidis, Spyridon and Brown, Billyde and Gray, Darren W. and Shields, Niall and Sayers, Ríona and Mooney, Mark H. and O'Riordan, Alan and et al.}, year={2017}, month={Aug}, pages={073701} }
 @article{pavlidis_alexopoulos_ulusoy_cho_papapolymerou_2017, title={Encapsulated Organic Package Technology for Wideband Integration of Heterogeneous MMICs}, volume={65}, ISSN={0018-9480 1557-9670}, url={http://dx.doi.org/10.1109/tmtt.2016.2630067}, DOI={10.1109/tmtt.2016.2630067}, abstractNote={The heterogeneous integration of silicon germanium (SiGe) and gallium arsenide (GaAs) technologies is presented using a novel encapsulated packaging approach with organic laminates. The combination of unique and optimally matched interconnects for each die, and the low-loss nature of the organic substrates, provides wideband performance and system design flexibility. A hybrid receiver front-end is realized on multilayer Rogers RO3003 to demonstrate this concept, incorporating a flip-chip bonded SiGe low-noise amplifier and a ribbon-bonded GaAs mixer. The simulated 3-dB bandwidth of the receiver is 4.5–14.5 GHz with a maximum conversion gain of 1.2 dB. Measured results for the packaged module show a 4–14-GHz 3-dB bandwidth and 0.9-dB maximum conversion gain. These results validate that the package is indeed low loss and preserves system performance over the entire bandwidth. The receiver also exhibits a double side band NFmin of 4 dB and a maximum  $P_{\text {1 dB, input}}$  of −5.5 dBm. This is the first time that heterogeneous semiconductor technologies have been integrated and encapsulated within a multilayer organic package using different interconnects for each chip to form a receiver. Moreover, the receiver achieves the widest bandwidth among heterogeneous receivers reported to date.}, number={2}, journal={IEEE Transactions on Microwave Theory and Techniques}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Pavlidis, Spyridon and Alexopoulos, George and Ulusoy, Ahmet Cagri and Cho, Moon-Kyu and Papapolymerou, John}, year={2017}, month={Feb}, pages={438–448} }
 @article{kim_alrowais_pavlidis_brand_2016, title={Size-Scalable and High-Density Liquid-Metal-Based Soft Electronic Passive Components and Circuits Using Soft Lithography}, volume={27}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/adfm.201604466}, DOI={10.1002/adfm.201604466}, abstractNote={The use of conducting liquids with high electrical conductivity, such as eutectic gallium–indium (EGaIn), has great potential in electronics applications requiring stretchability and deformability beyond conventional flexible electronics relying on solid conductors. An advanced liquid metal thin‐line patterning process based on soft lithography and a compatible vertical integration technique are presented that enable size‐scalable and high‐density EGaIn‐based, soft microelectronic components and circuits. The advanced liquid metal thin‐line patterning process based on poly(dimethylsiloxane) (PDMS) substrates and soft lithography techniques allows for simultaneous patterning of uniform and residue‐free EGaIn lines with line width from single micrometers to several millimeters at room temperature and under ambient pressure. Using this fabrication technique, passive electronic components and circuits are investigated under elastic deformations using numerical and experimental approaches. In addition, soft through‐PDMS vias with high aspect ratio are demonstrated for multilayer interconnections in 2.5D and 3D integration approaches. To highlight the system‐level potential of the patterning technique, a chemical sensor based on an integrated LC resonance circuit with a microfluidic‐tunable interdigitated capacitor and a planar spiral inductor is fabricated and characterized. Finally, to show the flexibility and stretchability of the resulting electronics, circuits with embedded light emitting diodes (LEDs) are investigated under bending, twisting, and stretching deformations.}, number={3}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Kim, Min-gu and Alrowais, Hommood and Pavlidis, Spyridon and Brand, Oliver}, year={2016}, month={Nov}, pages={1604466} }