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1. A Compact Model for Polarization-Graded HEMTs Demonstrating Enhanced Linearity

   https://doi.org/10.1109/TED.2025.3592176  

   Nazir, Mohammad_Sajid; Mohammad_Shayoub, Mir; Venkatesan, Nivedhita; Fay, Patrick; Singh_Chauhan, Yogesh (September 2025, IEEE Transactions on Electron Devices)

   This article presents an approach for modeling polarization-graded gallium nitride (GaN) high-electron-mobility transistors (HEMTs). Unlike conventional GaN HEMTs, where a 2-D electron gas (2DEG) forms at the barrier–channel interface, graded structures feature a 3-D electron distribution. TCAD simulations are used to extract carrier density and energy band diagrams, which form the basis for model development. The derivation uses refined approximations for the Fermi–Dirac integral solu- tion, ensuring differentiability while accurately correlating carrier density with the applied gate bias through the use of potential balance. A surface-potential-based approach is subsequently used to model terminal currents and charges. Validation of the model is done through comparison with on-wafer measurements and published data, including dc transfer and output characteristics and measured S-parameters over the frequency range of 10 MHz–110 GHz. Furthermore, model accuracy in representing linearity is verified by comparing to large signal and intermodulation measurements at 10 GHz. 

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2. Characterization of Thermal Stability and Unexpected Mobility Enhancement in IGZO FETs Measured Up to 750 °C

   https://doi.org/10.1109/LED.2026.3656803  

   Nam, Kisoo; Niu, Chang; Jang, Hyeongjun; Park, Beomjin; Park, Yoonju; Lee, Youngjoon; Alam, Muhammad A; Jeong, Changwook; Ye, Peide D (March 2026, IEEE Electron Device Letters)

   In this work, we report the in-situ high-temperature electrical characteristics of atomic-layer-deposited (ALD) InGaZnO (IGZO) field-effect transistors (FETs). Transfer characteristics of IGZO FETs are measured up to 750 ℃, where crystallization of the gate dielectric leads to degradation of transistor switching performance. Remarkably, the oxide channel material remains functional, and the FETs exhibit minimal degradation after 90 minutes at 600 ℃, demonstrating the exceptional thermal stability of channel performance. An unexpected mobility enhancement is observed with increasing temperature. With the peak field effect mobility (µFE) of 154 cm²V⁻¹s⁻¹ at 550 ℃, this temperature-dependence contrasts with that of conventional single-crystal wide bandgap materials. The mobility enhancement is consistent with our nanocrystalline mobility model, which incorporates grain boundary (GB) scattering. At elevated temperatures, de-trapped defects transition into trapped states that no longer capture carriers, reducing the energy barrier (Eb) at the grain boundaries and enhancing mobility. Furthermore, the contact resistance (Rc) and sheet resistance (Rsh) are reduced by 81% and 72%, respectively, at 600 ℃. This result underscores the strong potential of ALD oxide semiconductor FETs for Dynamic Random Access Memory (DRAM) and extreme-environment electronics. 

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3. Atomic layer self-transducing MoS2 vibrating channel transistors with 0.5 pm/Hz1/2 displacement sensitivity at room temperature

   https://doi.org/10.1063/5.0170127  

   Yousuf, S_M_Enamul Hoque; Feng, Philip X-L (January 2024, Applied Physics Letters)

   We report on the experimental demonstration of high-performance suspended channel transistors with single- and bilayer (1L and 2L) molybdenum disulfide (MoS2), and on operating them as vibrating channel transistors (VCTs) and exploiting their built-in dynamic electromechanical coupling to read out picoampere (pA) transconduction current directly at the vibrating tones, without frequency conversion or down-mixing, for picometer (pm)-scale motion detection at room temperature. The 1L- and 2L-MoS2 VCTs exhibit excellent n-type transistor behavior with high mobility [150 cm2/(V·s)] and small subthreshold swing (98 mV/dec). Their resonance motions are probed by directly measuring the small-signal drain-source currents (iD). Electromechanical characteristics of the devices are extracted from the measured iD, yielding resonances at f0 = 31.83 MHz with quality factor Q = 117 and f0 = 21.43 MHz with Q = 110 for 1L- and 2L-MoS2 VCTs, respectively. The 2L-MoS2 VCT demonstrates excellent current and displacement sensitivity (Si1/2 = 2 pA/Hz1/2 and Sx1/2 = 0.5 pm/Hz1/2). We demonstrate f0 tuning by controlling gate voltage VG and achieve frequency tunability Δf0/f0 ≈ 8% and resonance frequency change Δf0/ΔVG ≈ 0.53 kHz/mV. This study helps pave the way to realizing ultrasensitive self-transducing 2D nanoelectromechanical systems at room temperature, in all-electronic configurations, for on-chip applications. 

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4. A 0.4–1.2 GHz SiGe Cryogenic LNA for Readout of MKID Arrays

   Hosseini, Mohsen; Wong, Wei-Ting; Bardin, Joseph (January 2019, 2019 IEEE/MTT-S International Microwave Symposium)

   The design and characterization of a low noise amplifier optimized for the readout of microwave kinetic inductance detectors is described. The work is first motivated through a description of microwave kinetic inductance detectors and a discussion of the requirements for the low-noise amplifiers employed for readout of these devices. Next, the design of a two-stage silicon germanium cryogenic integrated circuit low noise amplifier is presented. The small-signal and large-signal characteristics of the fabricated amplifier are then measured. It is shown that, at a physical temperature of 16 K, the amplifier achieves a gain of greater than 30 dB and an average noise temperature of 3.3 K over the 0.4–1.2 GHz frequency band while dissipating less than 7 mW. Moreover, the wideband compression characteristics are measured it is found that the linearity of the amplifier is sufficient to support frequency domain multiplexed readout of more than 500 detectors. 

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5. Thin channel Ga2O3 MOSFET with 55 GHz fMAX and > 100 V breakdown

   https://doi.org/10.1063/5.0208580  

   Saha, Chinmoy Nath; Vaidya, Abhishek; Nipu, Noor Jahan; Meng, Lingyu; Yu, Dong Su; Zhao, Hongping; Singisetti, Uttam (August 2024, Applied Physics Letters)

   This Letter reports a highly scaled 90 nm gate length β-Ga2O3 (Ga2O3) T-gate MOSFET with a power gain cutoff frequency (fMAX) of 55 GHz. The 60 nm thin epitaxial Ga2O3 channel layer was grown by molecular beam epitaxy, while the highly doped (n++) source/drain regions were regrown using metal organic chemical vapor deposition. Maximum on current (IDS,MAX) of 160 mA/mm and trans-conductance (gm) around 36 mS/mm were measured at VDS = 10 V for LSD = 1.5 μm device. Transconductance and on current are limited by high channel sheet resistance (Rsheet). Gate/drain breakdown voltage of 125 V was measured for LGD = 1.2 μm. We extracted 27 GHz current gain cutoff frequency (fT) and 55 GHz fMAX for 20 V drain bias for unpassivated devices. While no current collapse was seen initially for both drain and gate lag measurements for 500 ns pulse, moderate current collapse was observed after DC, RF measurements caused by electrical stressing. We calculated a high fT. VBR product of 3.375 THz V, which is comparable to the state-of-the-art GaN HEMTs. This figure of merit suggests that Ga2O3 could be a potential candidate for X-band application. 

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