@article{sengupta_little_mita_markham_dycus_stein_wu_sitar_kish_pavlidis_2024, title={Wafer-bonded In<sub>0.53</sub>Ga<sub>0.47</sub>As/GaN p-n diodes with near-unity ideality factor}, volume={125}, ISSN={["1077-3118"]}, DOI={10.1063/5.0194526}, abstractNote={III–V/III-nitride p–n junctions were realized via crystal heterogeneous integration, and the resulting diodes were characterized to analyze electrical behavior and junction quality. p-type In0.53Ga0.47As, which is a well-established base layer in InP heterojunction bipolar transistor (HBT) technology, was used in combination with a homoepitaxial n-type GaN. The latter offers low dislocation density, coupled with high critical electric field and saturation velocity, which are attractive for use in future HBT collector layers. Transmission electron microscopy confirms an abrupt interface in the fabricated heterogeneous diodes. Electrical characterization of the diodes reveals a near-unity ideality factor (n ∼ 1.07) up to 145 °C, a high rectification ratio of ∼108, and a low interface trap density of 3.7 × 1012 cm−2.}, number={6}, journal={APPLIED PHYSICS LETTERS}, author={Sengupta, Rohan and Little, Brian and Mita, Seiji and Markham, Keith and Dycus, J. Houston and Stein, Shane and Wu, Barry and Sitar, Zlatko and Kish, Fred and Pavlidis, Spyridon}, year={2024}, month={Aug} }
 @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.}, number={3}, 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{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"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85151776292&partnerID=MN8TOARS}, DOI={10.35848/1882-0786/acc443}, abstractNote={Abstract
               We investigate the electrical characteristics of Ni Schottky contacts on n-type GaN films that have undergone ultra-high-pressure annealing (UHPA), a key processing step for activating implanted Mg. Contacts deposited on these films exhibit low rectification and high leakage current compared to contacts on as-grown films. By employing an optimized surface treatment to restore the GaN surface following UHPA, we obtain Schottky contacts with a high rectification ratio of ∼109, a near-unity ideality factor of 1.03, and a barrier height of ∼0.9 eV. These characteristics enable the development of GaN junction barrier Schottky diodes employing Mg implantation and UHPA.}, 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
               We present a comprehensive performance analysis of vertical GaN JFETs via TCAD simulation with unique considerations for gates formed by Mg ion implantation into GaN. The dependence of the specific ON-resistance and pinch-off voltage on the gate and channel design parameters is first evaluated for a JFET with abrupt gate-channel junctions. Then, the influence of the gate acceptor concentration and distribution is studied to elucidate the consequences of incomplete acceptor activation or acceptor diffusion resulting from specialized post-implantation annealing techniques necessary for the activation of p-GaN. Examples of normally-ON and normally-OFF designs with 1.7 kV breakdown voltage for 1.2 kV applications are chosen for the activation and diffusion studies to demonstrate how the pinch-off and conduction characteristics are affected for different channel widths and doping concentrations conducive to each type of operation. Record low specific ON-resistance below 1 mΩ cm2 is predicted for both, but gate acceptor diffusion increases the channel resistance, especially for JFETs designed to be normally-OFF.}, number={12}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Stein, Shane R. and Khachariya, Dolar and Pavlidis, Spyridon}, year={2022}, month={Dec} }
 @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"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85139392288&partnerID=MN8TOARS}, DOI={10.35848/1882-0786/ac8f81}, abstractNote={Abstract
               We report a kV class, low ON-resistance, vertical GaN junction barrier Schottky (JBS) diode with selective-area p-regions formed via Mg implantation followed by high-temperature, ultra-high pressure (UHP) post-implantation activation anneal. The JBS has an ideality factor of 1.03, a turn-on voltage of 0.75 V, and a specific differential ON-resistance of 0.6 mΩ·cm2. The breakdown voltage of the JBS diode is 915 V, corresponding to a maximum electric field of 3.3 MV cm−1. These results underline that high-performance GaN JBS can be realized using Mg implantation and high-temperature UHP post-activation anneal.}, 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{stein_robbins_reddy_collazo_pavlidis_2021, title={UV illumination effects on AlGaN/GaN HEMTs for tunable RF oscillators}, volume={2021-January}, ISSN={["2164-2958"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85102009293&partnerID=MN8TOARS}, 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} }