@article{bagheri_klump_washiyama_breckenridge_kim_guan_khachariya_quinones-garcia_sarkar_rathkanthiwar_et al._2022, title={Doping and compensation in heavily Mg doped Al-rich AlGaN films}, volume={120}, ISSN={["1077-3118"]}, DOI={10.1063/5.0082992}, abstractNote={Record low resistivities of 10 and 30 Ω cm and room-temperature free hole concentrations as high as 3 × 1018 cm−3 were achieved in bulk doping of Mg in Al0.6Ga0.4N films grown on AlN single crystalline wafer and sapphire. The highly conductive films exhibited a low ionization energy of 50 meV and impurity band conduction. Both high Mg concentration (>2 × 1019 cm−3) and low compensation were required to achieve impurity band conduction and high p-type conductivity. The formation of VN-related compensators was actively suppressed by chemical potential control during the deposition process. This work overcomes previous limitations in p-type aluminum gallium nitride (p-AlGaN) and offers a technologically viable solution to high p-conductivity in AlGaN and AlN.}, number={8}, journal={APPLIED PHYSICS LETTERS}, author={Bagheri, Pegah and Klump, Andrew and Washiyama, Shun and Breckenridge, M. Hayden and Kim, Ji Hyun and Guan, Yan and Khachariya, Dolar and Quinones-Garcia, Cristyan and Sarkar, Biplab and Rathkanthiwar, Shashwat and et al.}, year={2022}, month={Feb} }
 @article{mukhopadhyay_lyle_pal_das_porter_sarkar_2022, title={Evidence of thermionic emission in forward biased beta-Ga2O3 Schottky diodes at Boltzmann doping limit}, volume={131}, ISSN={["1089-7550"]}, DOI={10.1063/5.0068211}, abstractNote={A near-ideal and homogeneous β-Ga2O3 Schottky diode with Co contact for a doping level of ∼4.2 × 1017 cm−3 in the drift layer where the Boltzmann approximation is valid is reported. Unlike Si or GaN, thermionic emission is shown to be the dominant current conduction mechanism in the β-Ga2O3 Schottky diode at this doping level. A wide depletion region appended with a large built-in potential is observed to limit the thermionic field emission current, which is otherwise evident in narrower bandgap semiconductor (such as Si or GaN) Schottky diodes having a similar carrier concentration in the drift region. The results shown in this study can be used to identify the theoretical limits of drift layer doping beyond which the ideality factor and reverse leakage current should start deteriorating in ultra-wide bandgap semiconductor based Schottky diodes.}, number={2}, journal={JOURNAL OF APPLIED PHYSICS}, author={Mukhopadhyay, Swarnav and Lyle, Luke A. M. and Pal, Hridibrata and Das, Kalyan K. and Porter, Lisa M. and Sarkar, Biplab}, year={2022}, month={Jan} }
 @article{jadhav_bagheri_klump_khachariya_mita_reddy_rathkanthiwar_kirste_collazo_sitar_et al._2022, title={On electrical analysis of Al-rich p-AlGaN films for III-nitride UV light emitters}, volume={37}, ISSN={["1361-6641"]}, url={https://doi.org/10.1088/1361-6641/ac3710}, DOI={10.1088/1361-6641/ac3710}, abstractNote={Abstract}, number={1}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, publisher={IOP Publishing}, author={Jadhav, Aakash and Bagheri, Pegah and Klump, Andrew and Khachariya, Dolar and Mita, Seiji and Reddy, Pramod and Rathkanthiwar, Shashwat and Kirste, Ronny and Collazo, Ramon and Sitar, Zlatko and et al.}, year={2022}, month={Jan} }
 @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{kirste_sarkar_reddy_guo_collazo_sitar_2021, title={Status of the growth and fabrication of AlGaN-based UV laser diodes for near and mid-UV wavelength}, volume={12}, ISSN={["2044-5326"]}, DOI={10.1557/s43578-021-00443-8}, abstractNote={In this article, the development of mid-UV laser diodes based on the AlGaN materials system is reviewed. The targeted wavelength for these lasers covers the range from 200 to 350 nm. After introducing UV laser diodes and explaining their applications, the challenges in growth, design, and fabrication are discussed. In addition, recent results from optically and electrically injected UV laser diodes are presented. Finally, we will discuss possible pathways to improve performance and give an outlook on the expected development of UV laser diodes in the near future. Graphical abstract}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Kirste, Ronny and Sarkar, Biplab and Reddy, Pramod and Guo, Qiang and Collazo, Ramon and Sitar, Zlatko}, year={2021}, month={Dec} }
 @article{amano_collazo_santi_einfeldt_funato_glaab_hagedorn_hirano_hirayama_ishii_et al._2020, title={The 2020 UV emitter roadmap}, volume={53}, ISSN={["1361-6463"]}, DOI={10.1088/1361-6463/aba64c}, abstractNote={Solid state UV emitters have many advantages over conventional UV sources. The (Al,In,Ga)N material system is best suited to produce LEDs and laser diodes from 400 nm down to 210 nm—due to its large and tuneable direct band gap, n- and p-doping capability up to the largest bandgap material AlN and a growth and fabrication technology compatible with the current visible InGaN-based LED production. However AlGaN based UV-emitters still suffer from numerous challenges compared to their visible counterparts that become most obvious by consideration of their light output power, operation voltage and long term stability. Most of these challenges are related to the large bandgap of the materials. However, the development since the first realization of UV electroluminescence in the 1970s shows that an improvement in understanding and technology allows the performance of UV emitters to be pushed far beyond the current state. One example is the very recent realization of edge emitting laser diodes emitting in the UVC at 271.8 nm and in the UVB spectral range at 298 nm. This roadmap summarizes the current state of the art for the most important aspects of UV emitters, their challenges and provides an outlook for future developments.}, number={50}, journal={JOURNAL OF PHYSICS D-APPLIED PHYSICS}, author={Amano, Hiroshi and Collazo, Ramon and Santi, Carlo De and Einfeldt, Sven and Funato, Mitsuru and Glaab, Johannes and Hagedorn, Sylvia and Hirano, Akira and Hirayama, Hideki and Ishii, Ryota and et al.}, year={2020}, month={Dec} }
 @article{bryan_bryan_washiyama_reddy_gaddy_sarkar_breckenridge_guo_bobea_tweedie_et al._2018, title={Doping and compensation in Al-rich AlGaN grown on single crystal AlN and sapphire by MOCVD}, volume={112}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/1.5011984}, DOI={10.1063/1.5011984}, abstractNote={In order to understand the influence of dislocations on doping and compensation in Al-rich AlGaN, thin films were grown by metal organic chemical vapor deposition (MOCVD) on different templates on sapphire and low dislocation density single crystalline AlN. AlGaN grown on AlN exhibited the highest conductivity, carrier concentration, and mobility for any doping concentration due to low threading dislocation related compensation and reduced self-compensation. The onset of self-compensation, i.e., the “knee behavior” in conductivity, was found to depend only on the chemical potential of silicon, strongly indicating the cation vacancy complex with Si as the source of self-compensation. However, the magnitude of self-compensation was found to increase with an increase in dislocation density, and consequently, AlGaN grown on AlN substrates demonstrated higher conductivity over the entire doping range.}, number={6}, journal={APPLIED PHYSICS LETTERS}, publisher={AIP Publishing}, author={Bryan, Isaac and Bryan, Zachary and Washiyama, Shun and Reddy, Pramod and Gaddy, Benjamin and Sarkar, Biplab and Breckenridge, M. Hayden and Guo, Qiang and Bobea, Milena and Tweedie, James and et al.}, year={2018}, month={Feb} }
 @inproceedings{sarkar_reddy_klump_rounds_breckenridge_haidet_mita_kirste_collazo_sitar_2018, title={On Contacts to III-nitride deep-UV emitters}, url={http://dx.doi.org/10.1109/icmap.2018.8354575}, DOI={10.1109/icmap.2018.8354575}, abstractNote={Although contacts to III-nitride visible and UV-A based emitters has been well explored, understanding the contacts to III-nitride deep-UV emitters have attracted research attention recently. Owing to the wide bandgap, both n-type and p-type contact metallization techniques result in a Schottky barrier at the metal-semiconductor interface. A way to reduce the contact resistance is to achieve a higher free carrier concentration in the epitaxial layer. As a result, growth of III-nitride epitaxial layers on native substrates are providing pathways for significant performance improvement. However, understanding the contacts to deep-UV emitters grown on native substrates are necessary to allow further performance improvement.}, booktitle={2018 3rd International Conference on Microwave and Photonics (ICMAP)}, author={Sarkar, B. and Reddy, P. and Klump, A. and Rounds, R. and Breckenridge, M. R. and Haidet, B. B. and Mita, S. and Kirste, R. and Collazo, Ramon and Sitar, Z.}, year={2018} }
 @article{sarkar_mills_lee_pitts_misra_franzon_2018, title={On Using the Volatile Mem-Capacitive Effect of TiO2 Resistive Random Access Memory to Mimic the Synaptic Forgetting Process}, volume={47}, ISSN={["1543-186X"]}, DOI={10.1007/s11664-017-5914-x}, number={2}, journal={JOURNAL OF ELECTRONIC MATERIALS}, author={Sarkar, Biplab and Mills, Steven and Lee, Bongmook and Pitts, W. Shepherd and Misra, Veena and Franzon, Paul D.}, year={2018}, month={Feb}, pages={994–997} }
 @article{reddy_washiyama_mecouch_hernandez-balderrama_kaess_breckenridge_sarkar_haidet_franke_kohn_et al._2018, title={Plasma enhanced chemical vapor deposition of SiO2 and SiNx on AlGaN: Band offsets and interface studies as a function of Al composition}, volume={36}, ISSN={["1520-8559"]}, DOI={10.1116/1.5050501}, abstractNote={In this work, the authors characterized the interface of plasma enhanced chemical vapor deposition (PECVD) dielectrics, SiO2 and SiNx with AlGaN as a function of Al composition. SiO2 is found to exhibit type I straddled band alignment with positive conduction and valence band offsets for all Al compositions. However, the interface Fermi level is found to be pinned within the bandgap, indicating a significant density of interface states. Hence, SiO2 is found to be suitable for insulating layers or electrical isolation on AlGaN with breakdown fields between 4.5 and 6.5 MV cm−1, but an additional passivating interlayer between SiO2 and AlGaN is necessary for passivation on Al-rich AlGaN. In contrast, Si-rich PECVD SiNx is found to exhibit type II staggered band alignment with positive conduction band offsets and negative valence band offsets for Al compositions <40% and type I straddled band alignment with negative conduction and valence band offsets for Al compositions >40% and is, hence, found to be unsuitable for insulating layers or electrical isolation on Al-rich AlGaN in general. In contrast to passivating stoichiometric LPCVD Si3N4, no evidence for interface state reduction by depositing SiNx on AlGaN is observed.}, number={6}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Reddy, Pramod and Washiyama, Shun and Mecouch, Will and Hernandez-Balderrama, Luis H. and Kaess, Felix and Breckenridge, M. Hayden and Sarkar, Biplab and Haidet, Brian B. and Franke, Alexander and Kohn, Erhard and et al.}, year={2018}, month={Nov} }
 @article{rounds_sarkar_alden_guo_klump_hartmann_nagashima_kirste_franke_bickermann_et al._2018, title={The influence of point defects on the thermal conductivity of AlN crystals}, volume={123}, ISSN={["1089-7550"]}, DOI={10.1063/1.5028141}, abstractNote={The average bulk thermal conductivity of free-standing physical vapor transport and hydride vapor phase epitaxy single crystal AlN samples with different impurity concentrations is analyzed using the 3ω method in the temperature range of 30–325 K. AlN wafers grown by physical vapor transport show significant variation in thermal conductivity at room temperature with values ranging between 268 W/m K and 339 W/m K. AlN crystals grown by hydride vapor phase epitaxy yield values between 298 W/m K and 341 W/m K at room temperature, suggesting that the same fundamental mechanisms limit the thermal conductivity of AlN grown by both techniques. All samples in this work show phonon resonance behavior resulting from incorporated point defects. Samples shown by optical analysis to contain carbon-silicon complexes exhibit higher thermal conductivity above 100 K. Phonon scattering by point defects is determined to be the main limiting factor for thermal conductivity of AlN within the investigated temperature range.}, number={18}, journal={JOURNAL OF APPLIED PHYSICS}, author={Rounds, Robert and Sarkar, Biplab and Alden, Dorian and Guo, Qiang and Klump, Andrew and Hartmann, Carsten and Nagashima, Toru and Kirste, Ronny and Franke, Alexander and Bickermann, Matthias and et al.}, year={2018}, month={May} }
 @article{rounds_sarkar_sochacki_bockowski_imanishi_mori_kirste_collazo_sitar_2018, title={Thermal conductivity of GaN single crystals: Influence of impurities incorporated in different growth processes}, volume={124}, ISSN={["1089-7550"]}, DOI={10.1063/1.5047531}, abstractNote={The thermal conductivity of GaN crystals grown by different techniques is analyzed using the 3ω method in the temperature range of 30 K to 295 K. GaN wafers grown by the ammonothermal method show a significant variation in thermal conductivity at room temperature with values ranging between 164 W m−1 K−1 and 196 W m−1 K−1. GaN crystals produced with the sodium flux and hydride vapor phase epitaxy methods show results of 211 W m−1 K−1 and 224 W m−1 K−1, respectively, at room temperature. Analysis using secondary ion mass spectrometry indicates varying amounts of impurities between the respective crystals and explains the behavior of thermal conductivity trends in the samples. The observed difference between thermal conductivity curves suggests that scattering of phonons at point defects dominates the thermal conductivity of GaN within the investigated temperature range. Deviations of model curves from thermal conductivity measurements and disparities between modelled characteristic lengths and actual sample thicknesses indicate that phonon resonances are active in GaN.}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={Rounds, Robert and Sarkar, Biplab and Sochacki, Tomasz and Bockowski, Michal and Imanishi, Masayuki and Mori, Yusuke and Kirste, Ronny and Collazo, Ramon and Sitar, Zlatko}, year={2018}, month={Sep} }
 @article{rounds_sarkar_klump_hartmann_nagashima_kirste_franke_bickermann_kumagai_sitar_et al._2018, title={Thermal conductivity of single-crystalline AIN}, volume={11}, ISSN={["1882-0786"]}, DOI={10.7567/apex.11.071001}, abstractNote={The thermal conductivity of AlN single crystals grown by physical vapor transport (PVT) and hydride vapor phase epitaxy (HVPE) was measured in the range of 30 to 325 K by the 3ω method. The measured room-temperature thermal conductivity ranged from 268 to 374 W m−1 K−1. Higher thermal conductivity correlated with higher transparency at 265 nm and lower total impurity levels.}, number={7}, journal={APPLIED PHYSICS EXPRESS}, author={Rounds, Robert and Sarkar, Biplab and Klump, Andrew and Hartmann, Carsten and Nagashima, Toru and Kirste, Ronny and Franke, Alexander and Bickermann, Matthias and Kumagai, Yoshinao and Sitar, Zlatko and et al.}, year={2018}, month={Jul} }
 @article{sarkar_reddy_kaess_haidet_tweedie_mita_kirste_kohn_collazo_sitar_et al._2017, title={(Invited) Material Considerations for the Development of III-nitride Power Devices}, volume={80}, ISBN={["978-1-62332-476-6"]}, ISSN={["1938-6737"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85033580489&partnerID=MN8TOARS}, DOI={10.1149/08007.0029ecst}, abstractNote={With advancement in growth of native III-nitride substrates, remarkable progress has been made to extend the functionality of GaN based power electronic devices. The low dislocation epitaxial films grown on native substrates outperforms the films grown on foreign substrates. However, several material considerations has to be incorporated in order to exploit the full potential of GaN and AlxGa1-xN (0<x≤1) based power devices. This paper presents a review report on the development of III-nitride power devices grown on foreign and native (GaN and AlN) substrates. Discussion on state-of-the art epitaxial material quality, contact formation and surface treatments films are presented.}, number={7}, journal={GALLIUM NITRIDE AND SILICON CARBIDE POWER TECHNOLOGIES 7}, author={Sarkar, B. and Reddy, Pramod and Kaess, F. and Haidet, B.B. and Tweedie, J. and Mita, S. and Kirste, R. and Kohn, E. and Collazo, R. and Sitar, Z. and et al.}, year={2017}, pages={29–36} }
 @article{reddy_sarkar_kaess_gerhold_kohn_collazo_sitar_2017, title={Defect-free Ni/GaN Schottky barrier behavior with high temperature stability}, volume={110}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/1.4973762}, DOI={10.1063/1.4973762}, abstractNote={In this work, we report on defect-free homogeneous behavior of Ni Schottky contacts patterned on surface treated n-GaN by photolithography with unity ideality factor, high temperature stability, and low reverse leakage. The barrier height (0.7 eV) and ideality factor (1.02) are found to be independent of temperature, indicating a highly homogeneous contact. The contacts are found to be stable with no significant change in ideality factor or leakage current up to an annealing temperature of 600 °C. Temperature dependence of the reverse leakage current shows no evidence for the existence of surface defects that would provide leakage paths, and the behavior was modeled by ATLAS simulations with an ideal homogeneous barrier of 0.7 eV. Consequently, the forward and reverse bias characteristics are explained by a common set of parameters. The surface treatment after the development and prior to metallization included an acid-based surface treatment. X-ray photoelectron spectroscopy (XPS) studies indicate that the hydroxide-based development process during photolithography changes the nitride surface composition by introducing excess C that degrades the ideality factor and introduces barrier inhomogeneity and high leakage currents. XPS studies further demonstrate that the restoration of a stable, Ga-rich surface, similar to as-grown surface, occurs due to the acid-based surface treatment, which is responsible for the observed unity ideality factor, homogeneous barrier, low leakage current, and high temperature stability.}, number={1}, journal={APPLIED PHYSICS LETTERS}, publisher={AIP Publishing}, author={Reddy, Pramod and Sarkar, Biplab and Kaess, Felix and Gerhold, Michael and Kohn, Erhard and Collazo, Ramon and Sitar, Zlatko}, year={2017}, month={Jan} }
 @article{sarkar_mita_reddy_klump_kaess_tweedie_bryan_bryan_kirste_kohn_et al._2017, title={High free carrier concentration in p-GaN grown on AlN substrates}, volume={111}, ISSN={["1077-3118"]}, url={https://doi.org/10.1063/1.4995239}, DOI={10.1063/1.4995239}, abstractNote={A high free hole concentration in III-nitrides is important for next generation optoelectronic and high power electronic devices. The free hole concentration exceeding 1018 cm−3 and resistivity as low as 0.7 Ω cm are reported for p-GaN layers grown by metalorganic vapor phase epitaxy on single crystal AlN substrates. Temperature dependent Hall measurements confirmed a much lower activation energy, 60–80 mV, for p-GaN grown on AlN as compared to sapphire substrates; the lowering of the activation energy was due to screening of Coulomb potential by free carriers. It is also shown that a higher doping density (more than 5 × 1019 cm−3) can be achieved in p-GaN/AlN without the onset of self-compensation.}, number={3}, journal={APPLIED PHYSICS LETTERS}, publisher={AIP Publishing}, author={Sarkar, Biplab and Mita, Seiji and Reddy, Pramod and Klump, Andrew and Kaess, Felix and Tweedie, James and Bryan, Isaac and Bryan, Zachary and Kirste, Ronny and Kohn, Erhard and et al.}, year={2017}, month={Jul} }
 @article{haidet_sarkar_reddy_bryan_bryan_kirste_collazo_sitar_2017, title={Nonlinear analysis of vanadium- and titanium-based contacts to Al-rich n-AlGaN}, volume={56}, ISSN={["1347-4065"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85030640149&partnerID=MN8TOARS}, DOI={10.7567/jjap.56.100302}, abstractNote={In this work, we report on voltage dependent contact characteristics of Al-rich n-AlGaN due to the presence of a Schottky barrier at the metal–AlGaN interface. Current–voltage characteristics appear to be linear at low voltages, but a clear nonlinearity is evident at high voltages. Unlike Ga-rich n-AlGaN where V-based contact marginally outperforms the Ti-based contact, V-based contact to Al-rich n-AlGaN outperforms the Ti-based contact by ∼2 orders of magnitude for all voltage ranges. The improved performance of V-based contacts is likely due to a lower Schottky barrier and partly due to ease of formation of a low barrier V–AlGaN interface.}, number={10}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, publisher={Japan Society of Applied Physics}, author={Haidet, Brian B. and Sarkar, Biplab and Reddy, Pramod and Bryan, Isaac and Bryan, Zachary and Kirste, Ronny and Collazo, Ramon and Sitar, Zlatko}, year={2017}, month={Oct} }
 @article{sarkar_reddy_klump_kaess_rounds_kirste_mita_kohn_collazo_sitar_2017, title={On Ni/Au Alloyed Contacts to Mg-Doped GaN}, volume={47}, ISSN={0361-5235 1543-186X}, url={http://dx.doi.org/10.1007/S11664-017-5775-3}, DOI={10.1007/s11664-017-5775-3}, number={1}, journal={Journal of Electronic Materials}, publisher={Springer Nature}, author={Sarkar, Biplab and Reddy, Pramod and Klump, Andrew and Kaess, Felix and Rounds, Robert and Kirste, Ronny and Mita, Seiji and Kohn, Erhard and Collazo, Ramon and Sitar, Zlatko}, year={2017}, month={Sep}, pages={305–311} }
 @article{sarkar_haidet_reddy_kirste_collazo_sitar_2017, title={Performance improvement of ohmic contacts on Al-rich n-AlGaN grown on single crystal AlN substrate using reactive ion etching surface treatment}, volume={10}, ISSN={["1882-0786"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85021839341&partnerID=MN8TOARS}, DOI={10.7567/apex.10.071001}, abstractNote={Four orders of magnitude improvement in specific contact resistivity of Al-rich n-AlGaN grown on single crystal AlN substrates is achieved by surface treatment based on reactive ion etching (RIE). The ohmic contacts to as-grown Al-rich n-AlGaN/AlN exhibit a high contact resistance and nonlinearity due to a large Schottky barrier and low dislocation density. The RIE surface treatment reduces the barrier height at the free surface by ∼0.5 eV and is also expected to introduce a defective surface required for ohmic contact formation.}, number={7}, journal={APPLIED PHYSICS EXPRESS}, publisher={Japan Society of Applied Physics}, author={Sarkar, Biplab and Haidet, Brian B. and Reddy, Pramod and Kirste, Ronny and Collazo, Ramon and Sitar, Zlatko}, year={2017}, month={Jul} }
 @article{reddy_washiyama_kaess_breckenridge_hernandez-balderrama_haidet_alden_franke_sarkar_kohn_et al._2016, title={High temperature and low pressure chemical vapor deposition of silicon nitride on AlGaN: Band offsets and passivation studies}, volume={119}, ISSN={["1089-7550"]}, url={https://doi.org/10.1063/1.4945775}, DOI={10.1063/1.4945775}, abstractNote={In this work, we employed X-ray photoelectron spectroscopy to determine the band offsets and interface Fermi level at the heterojunction formed by stoichiometric silicon nitride deposited on AlxGa1-xN (of varying Al composition “x”) via low pressure chemical vapor deposition. Silicon nitride is found to form a type II staggered band alignment with AlGaN for all Al compositions (0 ≤ x ≤ 1) and present an electron barrier into AlGaN even at higher Al compositions, where Eg(AlGaN) > Eg(Si3N4). Further, no band bending is observed in AlGaN for x ≤ 0.6 and a reduced band bending (by ∼1 eV in comparison to that at free surface) is observed for x > 0.6. The Fermi level in silicon nitride is found to be at 3 eV with respect to its valence band, which is likely due to silicon (≡Si0/−1) dangling bonds. The presence of band bending for x > 0.6 is seen as a likely consequence of Fermi level alignment at Si3N4/AlGaN hetero-interface and not due to interface states. Photoelectron spectroscopy results are corroborated by current-voltage-temperature and capacitance-voltage measurements. A shift in the interface Fermi level (before band bending at equilibrium) from the conduction band in Si3N4/n-GaN to the valence band in Si3N4/p-GaN is observed, which strongly indicates a reduction in mid-gap interface states. Hence, stoichiometric silicon nitride is found to be a feasible passivation and dielectric insulation material for AlGaN at any composition.}, number={14}, journal={JOURNAL OF APPLIED PHYSICS}, publisher={AIP Publishing}, author={Reddy, Pramod and Washiyama, Shun and Kaess, Felix and Breckenridge, M. Hayden and Hernandez-Balderrama, Luis H. and Haidet, Brian B. and Alden, Dorian and Franke, Alexander and Sarkar, Biplab and Kohn, Erhard and et al.}, year={2016}, month={Apr} }
 @article{sarkar_lee_misra_2015, title={Understanding the gradual reset in Pt/Al2O3/Ni RRAM for synaptic applications}, volume={30}, ISSN={["1361-6641"]}, DOI={10.1088/0268-1242/30/10/105014}, abstractNote={In this work, a study has been performed to understand the gradual reset in Al2O3 resistive random-access memory (RRAM). Concentration of vacancies created during the forming or set operation is found to play a major role in the reset mechanism. The reset was observed to be gradual when a significantly higher number of vacancies are created in the dielectric during the set event. The vacancy concentration inside the dielectric was increased using a multi-step forming method which resulted in a diffusion-dominated gradual filament dissolution during the reset in Al2O3 RRAM. The gradual dissolution of the filament allows one to control the conductance of the dielectric during the reset. RRAM devices with gradual reset show excellent endurance and retention for multi-bit storage. Finally, the conductance modulation characteristics realizing synaptic learning are also confirmed in the RRAM.}, number={10}, journal={SEMICONDUCTOR SCIENCE AND TECHNOLOGY}, author={Sarkar, Biplab and Lee, Bongmook and Misra, Veena}, year={2015}, month={Oct} }
 @inproceedings{sarkar_lee_misra_2015, title={Understanding the influence of E-a and band-offset toward the conductance modulation in Al2O3 and HfO2 synaptic RRAM}, DOI={10.1109/drc.2015.7175599}, abstractNote={This work highlights the contribution of E<sub>a</sub> and band-offset toward conductance change in RRAM dielectrics. Both Al<sub>2</sub>O<sub>3</sub> and HfO<sub>2</sub> RRAM showed a gradual conductance change suitable for synaptic applications, and the lower E<sub>a</sub> of the dielectric helps in generating higher number of vacancies during set and higher band-offset of the dielectric limiting the TAT current during reset resulting in a higher conductance change in Al<sub>2</sub>O<sub>3</sub> RRAM compared to HfO<sub>2</sub> RRAM.}, booktitle={2015 73rd Annual Device Research Conference (DRC)}, author={Sarkar, B. and Lee, B. and Misra, Veena}, year={2015}, pages={149–150} }
 @article{sarkar_ramanan_jayanti_di spigna_lee_franzon_misra_2014, title={Dual Floating Gate Unified Memory MOSFET With Simultaneous Dynamic and Non-Volatile Operation}, volume={35}, ISSN={["1558-0563"]}, DOI={10.1109/led.2013.2289751}, abstractNote={Dual floating gate flash memory has been fabricated and characterized to show dynamic operation, non-volatile operation, and simultaneous dynamic and non-volatile operation. The gate stack consists of a thin dielectric separating two floating gates sandwiched between a tunnel dielectric and interpoly dielectric. The quality of the thin dielectric that separates the floating gates is of utmost importance to retain dynamic operation. In this letter, we investigate a dual floating gate memory transistor and show its potential to combine DRAM and flash functionality in the same device.}, number={1}, journal={IEEE ELECTRON DEVICE LETTERS}, author={Sarkar, Biplab and Ramanan, Narayanan and Jayanti, Srikant and Di Spigna, Neil and Lee, Bongmook and Franzon, Paul and Misra, Veena}, year={2014}, month={Jan}, pages={48–50} }
 @inproceedings{sarkar_lee_misra_2014, title={Implications of lower zero-field activation energy of dielectric in Al2O3/HfO2 bi-layer dielectric RRAM forming process}, volume={64}, number={14}, booktitle={Nonvolatile memories 3}, author={Sarkar, B. and Lee, B. and Misra, V.}, year={2014}, pages={41–46} }
 @inproceedings{sarkar_jayanti_spigna_lee_misra_franzon_2013, title={Investigation of intermediate dielectric for dual floating gate MOSFET}, DOI={10.1109/nvmts.2013.6851052}, abstractNote={A dual floating gate transistor offers potential as a unified memory, with simultaneous volatile and non-volatile storage. The quality of the dielectric between the two floating gates is critical to achieving the required dynamic cycle endurance. This paper reports on the results of early experiments into the material choice and process for this dielectric.}, booktitle={2013 13th Non-Volatile Memory Technology Symposium (NVMTS)}, author={Sarkar, B. and Jayanti, S. and Spigna, N. Di and Lee, B. and Misra, V. and Franzon, Paul}, year={2013} }