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1. Enhancement-Mode AlInN/GaN High-Electron-Mobility Transistors Enabled by Thermally Oxidized Gates

   https://doi.org/10.1109/TED.2023.3343313  

   Palmese, Elia; Xue, Haotian; Pavlidis, Spyridon; Wierer, Jonathan J. (January 2023, IEEE transactions on electron devices)

   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 O 2 , and a SiN x mask is used to achieve selective oxidization of the AlInN layer. For comparison, a standard Schottky gate and atomic layer deposition (ALD) Al 2 O 3 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 ( ∼ 2 × 10 −7 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 N 2 , retaining enhancement mode behavior and leading to a further positive shift in threshold voltage. 

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2. In operando cryo-STEM of pulse-induced charge density wave switching in TaS2

   https://doi.org/10.1038/s41467-023-44093-2  

   Hart, James L.; Siddique, Saif; Schnitzer, Noah; Funni, Stephen D.; Kourkoutis, Lena F.; Cha, Judy J. (December 2023, Nature Communications)

   Abstract The charge density wave material 1T-TaS₂exhibits a pulse-induced insulator-to-metal transition, which shows promise for next-generation electronics such as memristive memory and neuromorphic hardware. However, the rational design of TaS₂devices is hindered by a poor understanding of the switching mechanism, the pulse-induced phase, and the influence of material defects. Here, we operate a 2-terminal TaS₂device within a scanning transmission electron microscope at cryogenic temperature, and directly visualize the changing charge density wave structure with nanoscale spatial resolution and down to 300 μs temporal resolution. We show that the pulse-induced transition is driven by Joule heating, and that the pulse-induced state corresponds to the nearly commensurate and incommensurate charge density wave phases, depending on the applied voltage amplitude. With our in operando cryogenic electron microscopy experiments, we directly correlate the charge density wave structure with the device resistance, and show that dislocations significantly impact device performance. This work resolves fundamental questions of resistive switching in TaS₂devices, critical for engineering reliable and scalable TaS₂electronics. 

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3. Electrolyte-gated junctionless III-V Nanowire transistors: a TCAD-based evaluation

   https://doi.org/10.1007/s10825-025-02338-x  

   Islam, Muhammad Shaffatul; Manimaran, Nithil Harris; Abrand, Alireza; Morrell, John Wyatt; Kirmani, Ahmad R; Xu, Ke; Mohseni, Parsian K (August 2025, Journal of Computational Electronics)

   Abstract In this study, we explore the operation and performance of electrolyte-gated junctionless III-V nanowire (NW) transistors featuring compositionally graded In_xGa_1-xAs channels. These devices leverage the electric double-layer (EDL) gating mechanism at the electrolyte/semiconductor interface to achieve ultra-high charge carrier densities, surpassing those possible with conventional oxide dielectrics. Fermi–Dirac statistics are introduced by a numerical method to reproduce associated charge densities of EDL transistors. A 1 nm interfacial HfO₂layer is introduced to capture the electrostatics of the EDL, prevent charge transfer between the electrolyte and the semiconductor, and mimic the Stern layer. Device simulations are conducted to optimize the heterostructured NW composition and doping profile, followed by benchmarking against traditional HfO₂-gated structures. The EDL-gated device achieves anI_ON/I_OFFratio of 10⁶, with a subthreshold slope of 60 mV/dec and a threshold voltage of 0.31 V at a low drain voltage of 0.3 V, indicating a two-order magnitude improvement over conventional junctionless oxide-gated NW transistors. Computational methodologies include finite element modeling in COMSOL to extract voltage-dependent ion densities and subsequent device simulations using Silvaco's Atlas software. The results indicate that the optimized EDL-gated device exhibits superior electrostatic integrity and performance metrics compared to conventional gating methods. The findings underscore the potential of EDL gating in III-V NW configurations for advanced electronic applications, demonstrating significant improvements in switching characteristics and power efficiency. Further optimization and exploration of bias-dependent ionic concentrations and configurable device geometries highlight the robustness and scalability of this approach for next-generation low-power electronics. 

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4. Optoelectronic control of surface plasmon polaritons at metal-doped semiconductor interfaces

   https://doi.org/10.1088/2515-7647/adcfe1  

   Vinnakota, Raj K; Schliemann, Mayra M; Shahriar, Shaimum (May 2025, Journal of Physics: Photonics)

   Abstract We present a metal–semiconductor (M–S) based electro-optic modulator designed for functional plasmonic circuits, utilizing the active control of surface plasmon polaritons (SPPs) at M–S junction interfaces. Through self-consistent multiphysics simulations, including electromagnetic, thermal, and current–voltage (IV) characteristics, we estimate bias- and doping concentration-dependent SPP modulation and switching times. This study focuses on germanium-based Schottky contacts and can be extended to other semiconducting materials. We performed parametric analysis using the developed thermo-electro-optic model to identify device parameters and dimensions for enhanced optical confinement and faster operation. The studied device exhibits signal modulation exceeding −28 dB, responsivity greater than −1800 dB V⁻¹, and switching rates of 8 GHz, suggesting potential data rates above 16 Gbit s⁻¹. Additionally, frequency response analysis using the numerical model confirms the device’s electrical tunability and predicts a 3 dB bandwidth of up to 4 GHz. These findings highlight the significant potential of Schottky junctions as active components in the development of plasmonic-based integrated circuits. 

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5. Influence of electrical field on the susceptibility of gallium nitride transistors to proton irradiation

   https://doi.org/10.1088/1361-6463/ad3f29  

   Rasel, Md Abu; Schoell, Ryan; Smyth, Christopher M; Hattar, Khalid; Harris, C Thomas; Lu, Tzu-Ming; Haque, Aman; Wolfe, Douglas E; Ren, Fan; Pearton, Stephen J (April 2024, Journal of Physics D: Applied Physics)

   Abstract Radiation susceptibility of electronic devices is commonly studied as a function of radiation energetics and device physics. Often overlooked is the presence or magnitude of the electrical field, which we hypothesize to play an influential role in low energy radiation. Accordingly, we present a comprehensive study of low-energy proton irradiation on gallium nitride high electron mobility transistors (HEMTs), turning the transistor ON or OFF during irradiation. Commercially available GaN HEMTs were exposed to 300 keV proton irradiation at fluences varying from 3.76 × 10¹²to 3.76 × 10¹⁴cm², and the electrical performance was evaluated in terms of forward saturation current, transconductance, and threshold voltage. The results demonstrate that the presence of an electrical field makes it more susceptible to proton irradiation. The decrease of 12.4% in forward saturation and 19% in transconductance at the lowest fluence in ON mode suggests that both carrier density and mobility are reduced after irradiation. Additionally, a positive shift in threshold voltage (0.32 V and 0.09 V in ON and OFF mode, respectively) indicates the generation of acceptor-like traps due to proton bombardment. high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy analysis reveal significant defects introduction and atom intermixing near AlGaN/GaN interfaces and within the GaN layer after the highest irradiation dose employed in this study. According toin-situRaman spectroscopy, defects caused by irradiation can lead to a rise in self-heating and a considerable increase in (∼750 times) thermoelastic stress in the GaN layer during device operation. The findings indicate device engineering or electrical biasing protocol must be employed to compensate for radiation-induced defects formed during proton irradiation to improve device durability and reliability. 

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