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1. Dependence of carrier escape lifetimes on quantum barrier thickness in InGaN/GaN multiple quantum well photodetectors

   https://doi.org/10.1364/OE.399924  

   Chow, Yi_Chao; Lee, Changmin; Wong, Matthew_S; Wu, Yuh-Renn; Nakamura, Shuji; DenBaars, Steven_P; Bowers, John_E; Speck, James_S (July 2020, Optics Express)

   We reported significant improvements in device speed by reducing the quantum barrier (QB) thicknesses in the InGaN/GaN multiple quantum well (MQW) photodetectors (PDs). A 3-dB bandwidth of 700 MHz was achieved with a reverse bias of -6 V. Carrier escape lifetimes due to carrier trapping in the quantum wells (QWs) were obtained from both simulation and experimental fitting, identifying carrier trapping as the major speed limiting factor in the InGaN/GaN MQW PDs. 

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2. Impact of Solid-State Charge Injection on Spectral Photoresponse of NiO/Ga2O3 p–n Heterojunction

   https://doi.org/10.3390/condmat8040106  

   Schulte, Alfons; Modak, Sushrut; Landa, Yander; Atman, Atman; Li, Jian-Sian; Chiang, Chao-Ching; Ren, Fan; Pearton, Stephen J; Chernyak, Leonid (December 2023, Condensed Matter)

   Forward bias hole injection from 10-nm-thick p-type nickel oxide layers into 10-μm-thick n-type gallium oxide in a vertical NiO/Ga2O3 p–n heterojunction leads to enhancement of photoresponse of more than a factor of 2 when measured from this junction. While it takes only 600 s to obtain such a pronounced increase in photoresponse, it persists for hours, indicating the feasibility of photovoltaic device performance control. The effect is ascribed to a charge injection-induced increase in minority carrier (hole) diffusion length (resulting in improved collection of photogenerated non-equilibrium carriers) in n-type β-Ga2O3 epitaxial layers due to trapping of injected charge (holes) on deep meta-stable levels in the material and the subsequent blocking of non-equilibrium carrier recombination through these levels. Suppressed recombination leads to increased non-equilibrium carrier lifetime, in turn determining a longer diffusion length and being the root-cause of the effect of charge injection. 

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3. Electron mobility in monolayer WS2 encapsulated in hexagonal boron-nitride

   https://doi.org/10.1063/5.0039766  

   Wang, Y.; Sohier, T.; Watanabe, K.; Taniguchi, T.; Verstraete, M. J.; Tutuc, E. (March 2021, Applied Physics Letters)

   We report electron transport measurements in dual-gated monolayer WS2 encapsulated in hexagonal boron-nitride. Using gated Ohmic contacts that operate from room temperature down to 1.5 K, we measure the intrinsic conductivity and carrier density as a function of temperature and gate bias. Intrinsic electron mobilities of 100 cm2/(V s) at room temperature and 2000 cm2/(V s) at 1.5 K are achieved. The mobility shows a strong temperature dependence at high temperatures, consistent with phonon scattering dominated carrier transport. At low temperature, the mobility saturates due to impurity and long-range Coulomb scattering. First-principles calculations of phonon scattering in monolayer WS2 are in good agreement with the experimental results, showing we approach the intrinsic limit of transport in these two-dimensional layers. 

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4. Impact of Self-heating on Performance and Reliability in FinFET and GAAFET Designs

   https://doi.org/10.1109/ISQED.2019.8697786  

   Chhabria, Vidya A.; Sapatnekar, Sachin S. (March 2019, 20th International Symposium on Quality Electronic Design (ISQED))

   Modern transistors such as FinFETs and gate-all-around FETs (GAAFETs) suffer from excessive heat confinement due to their small size and three-dimensional geometries, with limited paths to the thermal ambient. This results in device self-heating, which can reduce speed, increase leakage, and accelerate aging. This paper characterizes the temperature for both the 7nm FinFET and 5nm GAAFET sub-structures and analyzes its impact on circuit performance (delay and power) and reliability (bias temperature instability, hot carrier injection, and electromigration). On average, logic gates in a circuit heat up by 12K for 7nm SOI FinFET and by 17K for 5nm GAAFET designs. This rise in temperature accelerates delay degradation due to bias temperature instability and hot carrier injection by up to 25% in FinFET and 39% in GAAFET designs, and also degrades the electromigration-induced time to failure of wires by up to 38% in SOI FinFET and 45% in GAAFET technologies. 

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5. Forward bias annealing of proton radiation damage in NiO/Ga ₂ O ₃ rectifiers

   https://doi.org/10.1088/1402-4896/ad5514  

   Li, Jian-Sian; Chiang, Chao-Ching; Wan, Hsiao-Hsuan; Rasel, Md_Abu Jafar; Haque, Aman; Kim, Jihyun; Ren, Fan; Chernyak, Leonid; Pearton, S J (June 2024, Physica Scripta)

   Abstract 17 MeV proton irradiation at fluences from 3–7 × 10¹³cm⁻²of vertical geometry NiO/β-Ga₂O₃heterojunction rectifiers produced carrier removal rates in the range 120–150 cm⁻¹in the drift region. The forward current density decreased by up to 2 orders of magnitude for the highest fluence, while the reverse leakage current increased by a factor of ∼20. Low-temperature annealing methods are of interest for mitigating radiation damage in such devices where thermal annealing is not feasible at the temperatures needed to remove defects. While thermal annealing has previously been shown to produce a limited recovery of the damage under these conditions, athermal annealing by minority carrier injection from NiO into the Ga₂O₃has not previously been attempted. Forward bias annealing produced an increase in forward current and a partial recovery of the proton-induced damage. Since the minority carrier diffusion length is 150–200 nm in proton irradiated Ga₂O₃, recombination-enhanced annealing of point defects cannot be the mechanism for this recovery, and we suggest that electron wind force annealing occurs. 

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