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46 results on '"Chaudhuri, Reet"'

1. High conductivity Polarization-induced 2D hole gases in Undoped GaN/AlN Heterojunctions enabled by Impurity Blocking Layers

Author

Chaudhuri, Reet, Chen, Zhen, Muller, David, Xing, Huili Grace, and Jena, Debdeep

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Applied Physics
Abstract

High-conductivity undoped GaN/AlN 2D hole gases (2DHGs), the p-type dual of the AlGaN/GaN 2D electron gases (2DEGs), have offered valuable insights into hole transport in GaN and enabled the first GaN GHz RF p-channel FETs. They are an important step towards high-speed and high-power complementary electronics with wide-bandgap semiconductors. These technologically and scientifically relevant 2D hole gases are perceived to be not as robust as the 2DEGs because structurally similar heterostructures exhibit wide variations of the hole density over $\Delta p_s >$ 7 x 10$^{13}$ cm$^{-2}$, and low mobilities. In this work, we uncover that the variations are tied to undesired dopant impurities such as Silicon and Oxygen floating up from the nucleation interface. By introducing impurity blocking layers (IBLs) in the AlN buffer layer, we eliminate the variability in 2D hole gas densities and transport properties, resulting in a much tighter-control over the 2DHG density variations to $\Delta p_s \leq$ 1 x 10$^{13}$ cm$^{-2}$ across growths, and a 3x boost in the Hall mobilities. These changes result in a 2-3x increase in hole conductivity when compared to GaN/AlN structures without IBLs., Comment: The following article has been accepted by Journal of Applied Physics. After it is published, it will be found at [https://aip.scitation.org/journal/jap]

Published
2021
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10. Molecular Beam Epitaxy Growth of Scandium Nitride on Hexagonal SiC, GaN, and AlN

Author

Casamento, Joseph, Wright, John, Chaudhuri, Reet, Xing, Huili Grace, and Jena, Debdeep

Subjects
Condensed Matter - Materials Science
Abstract

RF plasma assisted MBE growth of Scandium Nitride (ScN) thin films on GaN (0001)/SiC, AlN (0001)/Al2O3 and on 6H-SiC (0001) hexagonal substrates is found to lead to a face centered cubic (rock-salt) crystal structure with (111) out-of-plane orientation instead of hexagonal orientation. For the first time, cubic (111) twinned patterns in ScN are observed by in-situ electron diffraction during epitaxy, and the twin domains in ScN are detected by electron backscattered diffraction, and further corroborated with X-ray diffraction. The epitaxial ScN films display very smooth, sub nanometer surface roughness at a growth temperature of 750C. Temperature-dependent Hall-effect measurements indicate a constant high n-type carrier concentration of ~1x1020/cm3 and electron mobilities of ~ 20 cm2/Vs.

Published
2019
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11. Wurtzite Phonons and the Mobility of a GaN/AlN 2D Hole Gas

Author

Bader, Samuel James, Chaudhuri, Reet, Schubert, Martin, Then, Han Wui, Xing, Huili Grace, and Jena, Debdeep

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

To make complementary GaN electronics more than a pipe dream, it is essential to understand the low mobility of 2D hole gases in III-Nitride heterostructures. This work derives both the acoustic and optical phonon spectra present in one of the most prominent p-channel heterostructures (the all-binary GaN/AlN stack) and computes the interactions of these spectra with the 2D hole gas, capturing the temperature dependence of its intrinsic mobility. Finally, the effects of strain on the electronic structure of the confined 2D hole gas are examined and a means is proposed to engineer the strain to improve the 2D hole mobility for enhanced p-channel device performance, with the goal of enabling wide-bandgap CMOS.

Published
2019
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12. Gate-recessed E-mode p-channel HFET with high on-current based on GaN/AlN 2D hole gas

Author

Bader, Samuel James, Chaudhuri, Reet, Nomoto, Kazuki, Hickman, Austin, Chen, Zhen, Then, Han Wui, Muller, David A., Xing, Huili Grace, and Jena, Debdeep

Subjects
Physics - Applied Physics
Abstract

High-performance p-channel transistors are crucial to implementing efficient complementary circuits in wide-bandgap electronics, but progress on such devices has lagged far behind their powerful electron-based counterparts due to the inherent challenges of manipulating holes in wide-gap semiconductors. Building on recent advances in materials growth, this work sets simultaneous records in both on-current (10 mA/mm) and on-off modulation (four orders) for the GaN/AlN wide-bandgap p-FET structure. A compact analytical pFET model is derived, and the results are benchmarked against the various alternatives in the literature, clarifying the heterostructure trade-offs to enable integrated wide-bandgap CMOS for next-generation compact high-power devices.

Published
2018
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13. A polarization-induced 2D hole gas in undoped gallium nitride quantum wells

Author

Chaudhuri, Reet, Bader, Samuel James, Chen, Zhen, Muller, David A., Huili, Xing, and Jena, Debdeep

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The long-missing polarization-induced two-dimensional hole gas is finally observed in undoped gallium nitride quantum wells. Experimental results provide unambiguous proof that a 2D hole gas in GaN grown on AlN does not need acceptor doping, and can be formed entirely by the difference in the internal polarization fields across the semiconductor heterojunction. The measured 2D hole gas densities, about $4 \times 10^{13}$ cm$^{-2}$, are among the highest among all known semiconductors and remain unchanged down to cryogenic temperatures. Some of the lowest sheet resistances of all wide-bandgap semiconductors are seen. The observed results provide a new probe for studying the valence band structure and transport properties of wide-bandgap nitride interfaces, and simultaneously enable the missing component for gallium nitride-based p-channel transistors for energy-efficient electronics., Comment: 20 pages, 4 + 2 figures

Published
2018
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16. X-band epi-BAW resonators.

Author

Zhao, Wenwen, Asadi, Mohammad Javad, Li, Lei, Chaudhuri, Reet, Nomoto, Kazuki, Xing, Huili Grace, Hwang, James C. M., and Jena, Debdeep

Subjects
RESONATORS, ALUMINUM nitride, MICROWAVE filters, MODULATION-doped field-effect transistors, QUANTUM computing, ACOUSTIC resonators
Abstract

Using epitaxial aluminum nitride (AlN) developed for ultraviolet photonics and high-speed electronics, we demonstrate suspended AlN thin-film bulk acoustic resonators (FBARs) at 9.2 GHz in the X-band (8–12 GHz) of the microwave spectrum. The resonators show a Q m a x ≈ 614 and a figure of merit f ⋅ Q ≈ 5.6 THz. The material stack of these epi-AlN FBARs allows monolithic integration with AlN/GaN/AlN quantum well high-electron-mobility-transistors to a unique RF front end and also enable integration with epitaxial nitride superconductors for microwave filters for quantum computing. [ABSTRACT FROM AUTHOR]

Published
2022
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18. 15-GHz Epitaxial AlN FBARs on SiC Substrates

Author

Zhao, Wenwen, primary, Asadi, Mohammad Javad, additional, Li, Lei, additional, Chaudhuri, Reet, additional, Nomoto, Kazuki, additional, Xing, Huili Grace, additional, Hwang, James C. M., additional, and Jena, Debdeep, additional

Published
2023
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20. AlN/AlGaN/AlN quantum well channel HEMTs.

Author

Singhal, Jashan, Kim, Eungkyun, Hickman, Austin, Chaudhuri, Reet, Cho, Yongjin, Xing, Huili Grace, and Jena, Debdeep

Subjects
QUANTUM wells, MODULATION-doped field-effect transistors, HIGH voltages, OHMIC contacts, POWER electronics, THRESHOLD voltage
Abstract

We present a compositional dependence study of electrical characteristics of AlxGa1−xN quantum well channel-based AlN/AlGaN/AlN high electron mobility transistors (HEMTs) with x = 0.25 , 0.44 , and 0.58. This ultra-wide bandgap heterostructure is a candidate for next-generation radio frequency and power electronics. The use of selectively regrown n-type GaN Ohmic contacts results in contact resistance that increases as the Al content of the channel increases. The DC HEMT device characteristics reveal that the maximum drain current densities progressively reduce from 280 to 30 to 1.7 mA/mm for x = 0.25 , 0.44 , and 0.58, respectively. This is accompanied by a simultaneous decrease (in magnitude) in threshold voltage from −5.2 to −4.9 to −2.4 V for the three HEMTs. This systematic experimental study of the effects of Al composition x on the transistor characteristics provides valuable insights for engineering AlGaN channel HEMTs on AlN for extreme electronics at high voltages and high temperatures. [ABSTRACT FROM AUTHOR]

Published
2023
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26. Large Signal Response of AlN/GaN/AlN HEMTs at 30 GHz

Author

Hickman, Austin, primary, Chaudhuri, Reet, additional, Moser, Neil, additional, Elliott, Michael, additional, Nomoto, Kazuki, additional, Li, Lei, additional, Hwang, James C. M, additional, Grace Xing, Huili, additional, and Jena, Debdeep, additional

Published
2021
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31. Very High Density (>1014 cm−2) Polarization‐Induced 2D Hole Gases Observed in Undoped Pseudomorphic InGaN/AlN Heterostructures.

Author

Chaudhuri, Reet, Zhang, Zexuan, Xing, Huili Grace, and Jena, Debdeep

Subjects
INDIUM gallium nitride, HETEROSTRUCTURES, FIELD-effect transistors, CARRIER density, EPITAXY
Abstract

High hole densities are desired in p‐channel field effect transistors to improve the speed and on‐currents. Building on the recently discovered undoped, polarization‐induced GaN/AlN 2D hole gas (2DHG), this work demonstrates the tuning of the piezoelectric polarization difference across the heterointerface by introducing indium in the GaN channel. Using careful design and epitaxial growths, these pseudomorphic (In)GaN/AlN heterostructures result in some of the highest carrier densities of >1014 cm−2 in a III‐nitride heterostructure—just an order below the intrinsic crystal limit of ≈1015 cm−2. These ultra‐high density InGaN/AlN 2DHGs show room temperature mobilities of 0.5–4 cm2 V−1 s−1 and do not freeze out at low temperatures. A characteristic alloy fluctuation energy of 1.0 eV for hole scattering in InGaN alloy is proposed based on the experiments. [ABSTRACT FROM AUTHOR]

Published
2022
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32. Prospects for Wide Bandgap and Ultrawide Bandgap CMOS Devices

Author

Bader, Samuel James, primary, Lee, Hyunjea, additional, Chaudhuri, Reet, additional, Huang, Shimin, additional, Hickman, Austin, additional, Molnar, Alyosha, additional, Xing, Huili Grace, additional, Jena, Debdeep, additional, Then, Han Wui, additional, Chowdhury, Nadim, additional, and Palacios, Tomas, additional

Published
2020
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35. In Situ Crystalline AlN Passivation for Reduced RF Dispersion in Strained‐Channel AlN/GaN/AlN High‐Electron‐Mobility Transistors.

Author

Chaudhuri, Reet, Hickman, Austin, Singhal, Jashan, Casamento, Joseph, Xing, Huili Grace, and Jena, Debdeep

Subjects
*PASSIVATION, *MODULATION-doped field-effect transistors, *TWO-dimensional electron gas, *GALLIUM nitride, *SILICON nitride, *DISPERSION (Chemistry), *SURFACE states
Abstract

The recent demonstration of ≈2 W mm−1 output power at 94 GHz in AlN/GaN/AlN high‐electron‐mobility transistors (HEMTs) has established AlN as a promising platform for millimeter‐wave electronics. The current state‐of‐art AlN HEMTs using ex situ‐deposited silicon nitride (SiN) passivation layers suffer from soft gain compression due to trapping of carriers by surface states. Reducing surface state dispersion in these devices is thus desired to access higher output powers. Herein, a potential solution using a novel in situ crystalline AlN passivation layer is provided. A thick, 30+ nm‐top AlN passivation layer moves the as‐grown surface away from the 2D electron gas (2DEG) channel and reduces its effect on the device. Through a series of metal‐polar AlN/GaN/AlN heterostructure growths, it is found that pseudomorphically strained ≤15 nm thin GaN channels are crucial to be able to grow thick AlN barriers without cracking. The fabricated recessed‐gate HEMTs on an optimized heterostructure with 50 nm AlN barrier layer and 15 nm GaN channel layer show reduction in dispersion down to 2−6% compared with 20% in current state‐of‐art ex situ SiN‐passivated HEMTs. These results demonstrate the efficacy of this unique in situ crystalline AlN passivation technique and should unlock higher mm‐wave powers in next‐generation AlN HEMTs. [ABSTRACT FROM AUTHOR]

Published
2022
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38. (Invited) GaN-Based Multiple 2DEG Channel BRIDGE (Buried Dual Gate) HEMT Technology for High Power and Linearity

Author

Shinohara, Keisuke, primary, King, Casey, additional, Regan, Eric, additional, Gomez, M P, additional, Bergman, Joshua, additional, Carter, Andrew, additional, Arias, Andrea, additional, Urteaga, Miguel, additional, Brar, Berinder, additional, Page, Ryan, additional, Chaudhuri, Reet, additional, Islam, Moudud, additional, Xing, Huili Grace, additional, and Jena, Debdeep, additional

Published
2019
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43. (Invited) GaN-Based Multiple 2DEG Channel BRIDGE (Buried Dual Gate) HEMT Technology for High Power and Linearity

Author

Shinohara, Keisuke, King, Casey, Regan, Eric, Gomez, M P, Bergman, Joshua, Carter, Andrew, Arias, Andrea, Urteaga, Miguel, Brar, Berinder, Page, Ryan, Chaudhuri, Reet, Islam, Moudud, Grace, Huili, and, Xing, and Jena, Debdeep

Abstract

We report on a GaN-based field effect transistor with laterally-gated multiple 2DEG channels, called BRIDGE (buried dual gate) HEMT. Unique operation principle of the transistor enables unprecedented device characteristics suitable for efficient and linear millimeter-wave power amplifier applications. The lateral gate simultaneously modulate multiple 2DEG channels formed in an Al(Ga)N/GaN hetero-structure. A higher electron saturation velocity measured for a lower 2DEG density suggests that the multiple 2DEG channel structure is ideal for obtaining a high current density, and simultaneously enhancing high frequency performance of the transistor. The BRIDGE HEMTs built on a 16-channel HEMT epitaxial structure with a net 2DEG density of 3.3x1013 cm-2 exhibited a record high knee current density of 3.7 A/mm. The absence of the top contact gate results in negligible current collapse by eliminating a high electric field region at the drain end of the gate - another key feature of the BRIDGE HEMT.

Published
2019

44. RF operation of AlN/Al0.25Ga0.75N/AlN HEMTs with fT/fmaxof 67/166 GHz

Author

Kim, Eungkyun, Singhal, Jashan, Hickman, Austin, Li, Lei, Chaudhuri, Reet, Cho, Yongjin, Hwang, James C. M., Jena, Debdeep, and Xing, Huili Grace

Abstract

We report on highly-scaled Al0.25Ga0.75N channel high electron mobility transistors. Regrown ohmic contacts covering the sidewall of the compressively strained Al0.25Ga0.75N channel exhibited a low contact resistance of Rc= 0.23 Ω · mm. Scaled devices with a T-shaped gate showed record high speed for any AlGaN-based transistors, fT/fmax= 67/166 GHz, while simultaneously achieving high average breakdown field exceeding 2 MV cm−1. The load-pull measurements performed at 10 GHz revealed a 20% peak power added efficiency with an output power density of 2 W mm−1, which is mainly limited by the RF dispersion.

Published
2023
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45. Majestic progress: India's economy has come on in leaps and bounds overthe past 10 years, but companies on the subcontinent will have to move ever more quickly to keep up with the pace of change. Reet Chaudhuri, Manish Mohnot andNarayan Seshadri investigate the 'Red Queen effect'

Author

Chaudhuri, Reet, Mohnot, Manish, and Seshadri, Narayan

Subjects
India -- Economic aspects -- Economic policy, Economic conditions -- Forecasts and trends -- Economic aspects, Banking, finance and accounting industries, Business, Business, international, Market trend/market analysis, Economic aspects, Economic policy, Forecasts and trends
Abstract

'Well, in our county,' said Alice, still panting a little, 'you'd generally get to somewhere else if you ran very fast for a long time, as we've been doing.' 'A [...]

Published
2003

46. (Invited)GaN-Based Multiple 2DEG Channel BRIDGE (Buried Dual Gate) HEMT Technology for High Power and Linearity

Author

Shinohara, Keisuke, King, Casey, Regan, Eric, Gomez, M P, Bergman, Joshua, Carter, Andrew, Arias, Andrea, Urteaga, Miguel, Brar, Berinder, Page, Ryan, Chaudhuri, Reet, Islam, Moudud, Xing, Huili Grace, and Jena, Debdeep

Abstract

We report on a GaN-based field effect transistor with laterally-gated multiple 2DEG channels, called BRIDGE (buried dual gate) HEMT. Unique operation principle of the transistor enables unprecedented device characteristics suitable for efficient and linear millimeter-wave power amplifier applications. The lateral gate simultaneously modulate multiple 2DEG channels formed in an Al(Ga)N/GaN hetero-structure. A higher electron saturation velocity measured for a lower 2DEG density suggests that the multiple 2DEG channel structure is ideal for obtaining a high current density, and simultaneously enhancing high frequency performance of the transistor. The BRIDGE HEMTs built on a 16-channel HEMT epitaxial structure with a net 2DEG density of 3.3×1013cm-2exhibited a record high knee current density of 3.7 A/mm. The absence of the top contact gate results in negligible current collapse by eliminating a high electric field region at the drain end of the gate – another key feature of the BRIDGE HEMT.

Published
2019
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