arXiv subjects

Can Cao

Publications and source records attributed to Can Cao.

6 recordsLinked to original sources

arXiv2026

High Breakdown Field Multi-kV UWBG AlGaN Transistors

We demonstrate high-performance UWBG AlGaN PolFETs exhibiting a state-of-the-art combination of nearly 1 A/mm on-state current (~ 960 mA/mm) and large breakdown field (> 4.8 MV/cm) in high carrier density (1.15 x 1013 cm-2). Multi-kV robustness is successfully demonstrated exhibiting 1.28 and 2.17 kV by utilizing a gate-connected field plate structures in 3.9 and 6.8 {\mu}m LGD, corresponding to the extremely low specific on-resistance of 1.25 and 2.86 m{\Omega}cm2, respectively. High RF performance is also achieved, providing fT and fMAX, of 8.5 and 15 GHz, respectively, for 3.9 {\mu}m LGD. These results highlight UWBG AlGaN as a platform for both high-voltage RF and power applications.

physics.app-ph↗

arXiv2026

Microwave Performance of all MOCVD-grown AlScN/GaN MIS-HEMTs on Semi-Insulating GaN Substrates

We report on the design, fabrication, and characterization of all MOCVD-grown long-gate AlScN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) on semi-insulating GaN substrates. Devices with a gate length of $1~\mu$m and gate-drain spacing of $0.9~\mu$ m exhibit a maximum drain current density of 1 A/mm, an on/off current ratio of $2\times 10^5$, and a three-terminal breakdown voltage of 63 V. The device has near-ideal subthreshold characteristics with a subthreshold swing of 63 mV/dec and a current dispersion as low as 7.8$\%$ at 10 V due to the excellent interfacial quality with a trap density ($D_\mathrm{it}$) of $2.11\times{10}^{11}~\mathrm{cm}^{-2}eV^{-1}$ and the semi-insulating GaN substrate with a low threading dislocation density. Small-signal RF measurements reveal an $f_\mathrm{T}/f_\mathrm{max}$ of 25.8/51.1 GHz, while large-signal load-pull characterization at 10 GHz demonstrates an output power density of 4.04 W/mm with a power-added efficiency of 22.7$\%$. In addition, a minimum noise figure below 2.5 dB was measured over a wide drain current range from 100 mA/mm to 700 mA/mm below 6 GHz. These results extend previous demonstrations of short-gate MOCVD-grown AlScN/GaN HEMTs to the long-gate, high-voltage regime, confirming the robustness of this material system for both high-frequency and high-power device applications with favorable microwave noise performance.

physics.app-ph↗

arXiv2025

Ultra-Wide Bandgap AlGaN Heterostructure Field Effect Transistors with Current Gain Cutoff Frequency Above 85 GHz

We report the design and demonstration of ultra-wide-bandgap (UWBG) AlGaN polarization-graded field-effect transistors (PolFETs) that achieve a current-gain cutoff frequency above 85 GHz and a current density exceeding 1.3 A/mm. Ultra-thin channel and buffer layers were grown epitaxially on AlN substrates, and a reverse-graded AlGaN contact layer was incorporated to reduce the contact resistance to below 1 ohm.mm. With aggressively scaled device dimensions, the AlGaN PolFETs exhibit state-of-the-art high-frequency performance for UWBG transistors. Small-signal modeling reveals both parasitic and transit delays, confirming the benefits of reduced access resistance and enhanced intrinsic transconductance. These results establish a new performance benchmark for UWBG AlGaN devices and demonstrate their strong potential for next-generation millimeter-wave electronics.

physics.app-ph↗

arXiv2025

Scaled Ultra-Wide Bandgap AlGaN Polarization-Graded FET with Ultra-thin Buffer Layer

We report on the design and demonstration of ultra-wide bandgap AlGaN polarization-graded field effect transistors with ultra-thin channels to enable excellent current density and high-frequency performance while significantly reducing thermal resistance. We use polarization-graded AlGaN layers and ultra-thin pseudomorphic AlGaN buffer layers to enable low thermal resistance and excellent structural quality. The polarization-graded field effect transistors (PolFETs) demonstrated here show Imax over 800mA/mm and current/power gain cutoff frequency (fT/fmax) of 26/28 GHz. Small signal modeling and analysis were used to determine parasitic/transit delays, and gate-resistance thermometry was implemented to thermally characterize AlGaN PolFET and benchmark against state-of-the-art AlGaN HEMTs. The ultra-thin AlGaN PolFET showed thermal resistance of 12 K.mm/W, representing a significant reduction from typical AlGaN transistors. These results show state-of-art combination of high current density, excellent fT-LG product for ultra-wide bandgap AlGaN transistors, and superior thermal performance, and highlight the promise of AlGaN transistors for future RF and mm-wave applications.

physics.app-ph↗

arXiv2025

Barrier Electrostatics and Contact Engineering for Ultra-Wide Bandgap AlGaN HFETs

We report ultra-wide bandgap (UWBG) AlGaN heterostructure field-effect transistors (HFETs) exhibiting a high breakdown field (> 5.3 MV/cm) and a low contact resistance (~1.55 {\Omega}mm), tailored for high-power radiofrequency applications. A split-doped barrier architecture, employing two distinct doping concentrations, is shown to enhance both the breakdown field and contact resistance. This design enables a state-of-the-art combination of maximum drain current (487 mA/mm) and breakdown field, along with a high cutoff frequency of 7.2 GHz. These results demonstrate a viable pathway to push device performance toward the material limits while minimizing contact resistance in UWBG AlGaN HFETs, paving the way for next-generation high-power, high-frequency applications.

cond-mat.mtrl-sci↗

arXiv2025

Enhanced predictions of the Madden-Julian oscillation using the FuXi-S2S machine learning model: Insights into physical mechanisms

The Madden-Julian Oscillation (MJO) is the dominant mode of tropical atmospheric variability on intraseasonal timescales, and reliable MJO predictions are essential for protecting lives and mitigating impacts on societal assets. However, numerical models still fall short of achieving the theoretical predictability limit for the MJO due to inherent constraints. In an effort to extend the skillful prediction window for the MJO, machine learning (ML) techniques have gained increasing attention. This study examines the MJO prediction performance of the FuXi subseasonal-to-seasonal (S2S) ML model during boreal winter, comparing it with the European Centre for Medium- Range Weather Forecasts S2S model. Results indicate that for the initial strong MJO phase 3, the FuXi-S2S model demonstrates reduced biases in intraseasonal outgoing longwave radiation anomalies averaged over the tropical western Pacific (WP) region during days 15-20, with the convective center located over this area. Analysis of multiscale interactions related to moisture transport suggests that improvements could be attributed to the FuXi-S2S model's more accurate prediction of the area-averaged meridional gradient of low-frequency background moisture over the tropical WP. These findings not only explain the enhanced predictive capability of the FuXi-S2S model but also highlight the potential of ML approaches in advancing the MJO forecasting.

physics.ao-ph↗