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1. Ternary-containing Al _0.7 InAsSb digital alloys on InP and InP-on-Si [Invited]

   https://doi.org/10.1364/OME.567883  

   Wang, Ellie Y; Karimi, Hannaneh; Guzman, Francisco; Waqar, Moaz; Liu, Amy_W K; Fastenau, Joel M; Pan, Xiaoqing; Campbell, Joe C; Bank, Seth R (January 2025, Optical Materials Express)

   Al_xIn_1−xAs_ySb_1−yis a promising multiplier for avalanche photodiodes (APD) on InP for near-infrared applications. In this work, we investigated the potential of two different ternary-containing layer stacks for the growth of AlInAsSb digital alloys on InP and InP-on-Si templates with applications in future photodetectors. STEM measurements confirmed high-quality material and interfaces on both substrates with no evidence of phase separation. Low dark currents and high gains were measured from PIN diodes grown on both substrates, with slightly higher dark currents observed in the Si-based device due to defects resulting from lattice mismatch in the template. 

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2. Extension Doping with Low‐Resistance Contacts for P‐Type Monolayer WSe ₂ Field‐Effect Transistors

   https://doi.org/10.1002/aelm.202400843  

   Chen, Sihan; Zhang, Yue; King, William P; Bashir, Rashid; van_der_Zande, Arend M (December 2024, Advanced Electronic Materials)

   Abstract Source/Drain extension doping is crucial for minimizing the series resistance of the ungated channel and reducing the contact resistance of field‐effect transistors (FETs) in complementary metal–oxide–semiconductor (CMOS) technology. 2D semiconductors, such as MoS₂and WSe₂, are promising channel materials for beyond‐silicon CMOS. A key challenge is to achieve extension doping for 2D monolayer FETs without damaging the atomically thin material. This work demonstrates extension doping with low‐resistance contacts for monolayer WSe₂p‐FETs. Self‐limiting oxidation transforms a bilayer WSe₂into a hetero‐bilayer of a high‐work‐function WO_xSe_yon a monolayer WSe₂. Then, damage‐free nanolithography defines an undoped nano‐channel, preserving the high on‐current of WO_xSe_y‐doped FETs while significantly improving their on/off ratio. The insertion of an amorphous WO_xSe_yinterlayer under the contacts achieves record‐low contact resistances for monolayer WSe₂over a hole density range of 10¹²to 10¹³cm⁻²(1.2 ± 0.3 kΩ µm at 10¹³cm⁻²). The WO_xSe_y‐doped extension exhibits a sheet resistance as low as 10 ± 1 kΩ □⁻¹. Monolayer WSe₂p‐FETs with sub‐50 nm channel lengths reach a maximum drain current of 154 µA µm⁻¹with an on/off ratio of 10⁷–10⁸. These results define strategies for nanometer‐scale selective‐area doping in 2D FETs and other 2D architectures. 

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3. Uncooled GeSn MWIR Photodetectors Using Fully Relaxed Thin Triple‐Step Buffer

   https://doi.org/10.1002/admt.202500455  

   Park, Suho; Zhao, Haochen; Zhama, Tuofu; Chen, Zijun; Zhang, Yuying; Zhu, Xiaofeng; Prather, Dennis W; Kolodzey, James; Zeng, Yuping (June 2025, Advanced Materials Technologies)

   Abstract GeSn photodetectors monolithically grown on Ge virtual substrates demonstrate mid‐wave infrared (MWIR) detection at room temperature. The lattice mismatch between GeSn and Ge causes dislocations and compressive strain, creating leakage pathways and unwanted indirect band transitions. Designed thin Ge_0.91Sn_0.09triple‐step buffer layers of ≈175 nm total thickness reduce dislocations and enable full relaxation, showing 100% lattice relaxation and smooth surface roughness of 0.83 nm with shorter auto‐correlation length in surface morphology compared to single‐step buffers. Ge_1‐xSn_xphotodetectors (x= 0.09, 0.12, and 0.15) on triple‐step buffers withn‐i‐pconfigurations achieve lattice strain relaxations of 99%, 88%, and 80%, respectively. Ge_0.91Sn_0.09and Ge_0.88Sn_0.12show gradual variation in auto‐correlation amplitude, while Ge_0.85Sn_0.15shows an increase due to lattice mismatch. Shockley–Read–Hall recombination current dominates at low reverse bias due to mismatch‐induced dislocations, while band‐to‐band tunneling current dominates at higher reverse bias due to narrowing bandgap under strong electric fields. The photodetectors show extended spectral response with increasing Sn composition ofi‐GeSn active layer sandwiched by barriers. Ge_0.88Sn_0.12and Ge_0.85Sn_0.15exhibit extended wavelength cut‐offs of 3.12 and 3.27 µm at room temperature, demonstrating significant potential for silicon‐based MWIR applications. 

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4. Atmospheric effects on the laser-driven avalanche-based remote detection of radiation

   https://doi.org/10.1364/OL.488346  

   Zingale, A.; Waczynski, S.; Sears, J.; Lakis, R. E.; Milchberg, H. M. (January 2023, Optics Letters)

   The effect of realistic atmospheric conditions on mid-IR (λ = 3.9 µm) and long-wave-IR (λ = 10 µm) laser-induced avalanche breakdown for the remote detection of radioactive material is examined experimentally and with propagation simulations. Our short-range in-lab mid-IR laser experiments show a correlation between increasing turbulence level and a reduced number of breakdown sites associated with a reduction in the portion of the focal volume above the breakdown threshold. Simulations of propagation through turbulence are in excellent agreement with these measurements and provide code validation. We then simulate propagation through realistic atmospheric turbulence over a long range (0.1–1 km) in the long-wave-IR regime (λ = 10 µm). The avalanche threshold focal volume is found to be robust even in the presence of strong turbulence, only dropping by ∼50% over a propagation length of ∼0.6 km. We also experimentally assess the impact of aerosols on avalanche-based detection, finding that, while background counts increase, a useful signal is extractable even at aerosol concentrations 10 5 times greater than what is typically observed in atmospheric conditions. Our results show promise for the long-range detection of radioactive sources under realistic atmospheric conditions. 

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5. Advances in Se Wide‐Bandgap Photovoltaics and Te _x Se _1‐x SWIR Photodiodes

   https://doi.org/10.1002/advs.77340  

   Alfieri, Adam D; Jariwala, Deep (September 2026, Advanced Science)

   ABSTRACT Elemental selenium (Se), tellurium (Te), and their alloys (Te_xSe_1‐x) have re‐emerged over the past decade as a promising materials system for low‐cost and sustainable thin‐film optoelectronic devices. In particular, Se has become a promising material for wide bandgap photovoltaics (PVs), and Te_xSe_1‐xhas arisen as a high‐performance thin‐film option for infrared (IR) photodetectors. In this review, we focus on recent developments in Se PVs and Te_xSe_1‐xshort‐wave IR (SWIR) photodiodes (PDs). We discuss the motivations for pursuing these materials, the fundamental properties, considerations for toxicity and sustainability, and the advances in materials science and device engineering. Finally, we discuss open challenges and underexplored opportunities for further development. 

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