Metalenses which can freely manipulate light fields, are regarded as highly promising optical components for enhancing the performance of photodetectors. In this letter, a novel InGaAs/InP single-photon avalanche diode (SPAD) with small active diameter and backside InP metalens is presented. The active area, with a diameter of 8 mu m, is complemented by 100 mu m x100 mu m metalens that focuses incident photons into the photosensitive region. The focused beam size of the metalens is approximately 1.3 mu m (full width at half-maximum) at the target focal plane. The novel SPAD with backside metalens achieves a maximum photon detection efficiency (PDE) of 15.9% at wavelength of 1550 nm. Comparative experiments indicate that the integration of the metalens provides a 37% relative-increase in maximum PDE while maintaining a compact size. This work provides a new way for the realization of small-pixel, high-PDE InGaAs/InP SPAD arrays and supports the development of miniaturized, multi-dimensional photon detectors.

High-sensitivity, bias-selective dual-band infrared detection is essential for two-color absolute thermometry of mid- to long-wavelength infrared sources, including the picowatt-class signal regime relevant to cryogenic near-field thermal measurements. Here, we report a triple-quantum-well charge-sensitive infrared phototransistor in which two spatially isolated floating gates provide electrically separated photoresponse pathways, allowing the 10.1 and 16.4 μm channels to be addressed individually or jointly by gate bias. The cross-hole plasmonic grating supports two geometrically distinguishable resonances with different dominant tuning sensitivities: a period-dominated Rayleigh anomaly–surface plasmon polaritons (SPP) mode and an arm-length-dominated localized shape plasmon–SPP hybrid mode. This partially mode-decoupled response reduces spectral entanglement and enables practical co-design of the two infrared bands. At an optimized well doping of 8.0 × 1017 cm−3, the device delivers an integration responsivity of 6.17 × 105 A W−1 at VSD = 10 mV under a 4.24 pW, 300 K background; the band-resolved photocurrent responsivities at VSD = 120 mV are 1.35 × 103 A W−1 at 10.1 μm and 6.07 × 103 A W−1 at 16.4 μm. Quantum efficiencies of 19.4% (10.1 μm) and 16.0% (16.4 μm) yield specific detectivities of 8.5 × 1011 and 1.1 × 1012 cm Hz1/2 W−1, respectively, with a balanced (∼1:1) dual-band spectral response suitable for two-color pyrometry. The architecture establishes a route to high-gain dual-band mid- to long-wavelength infrared sensing for cryogenic two-color thermometry.

Enhancing electromagnetic coupling to achieve interaction between light and matter is imperative to develop high-performance terahertz devices. Here, we report an ultrasensitive terahertz detector based on the quasi-one-dimensional, low-energy Dirac Fermions in the topological semimetal-TaNiTe5, integrated with an asymmetric bow-tie antenna to enhance field localization and directional light coupling. The device operates via photothermoelectric (PTE) effect, enabling self-powered, homo/heterodyne dual-mode detection across from millimeter to terahertz band. It achieves room-temperature operation at 0.435 THz with a responsivity of 0.77 A/W, a noise equivalent power (NEP) below 9.71 pW·Hz1/2, a specific detectivity (D*) of 1.03 × 1011 Jones, and a response time less than 20 ns. Furthermore, owing to the unique electronic band structure and excellent carrier dynamics characteristics of the semimetal-TaNiTe5, the device enables heterodyne mixing with a radio frequency (RF) bandwidth exceeds 108 GHz, accompanied by intermediate frequency (IF) bandwidth >26.5 GHz. Leveraging its excellent performance, we demonstrate its potential for sub-THz communications and high-quality imaging in terms of encrypted data-information exchange. Our work establishes a strategy for achieving chip-level integration with versatile abilities for communication, and imaging at terahertz band.

InAsSb has emerged as a promising material for applications in infrared detection and advancing fundamental studies in condensed matter physics. However, the surface electronic properties of InAsSb remain insufficiently explored. In this work, high-quality InAsSb epilayers were grown using molecular beam epitaxy (MBE). Shubnikov-de Haas (SdH) oscillations and quantum Hall-like features were observed under low temperatures and high magnetic fields. Notably, linear magnetoresistance(LMR) was detected in the extreme quantum limit (EQL) even at elevated temperatures up to 250 K. The experimentally determined effective mass of the surface state electrons is 0.028 m0, which is 26 % smaller than that of the InAs surface state (0.038 m0). A Dingle ratio of 98 suggests that scattering is predominantly governed by long-range potentials and forward scattering, contributing to the observed high carrier mobility and pronounced quantum phenomena.

InAs nanowires (NWs) self-catalyzed grown on graphene surface frequently exhibit a large number of stacking-fault defects. However, the control of these defects in InAs NWs still remains a large challenge, which significantly limits the applications of InAs NWs in electronics and optoelectronics. In this work, the self-catalyzed growth of InAs NWs on graphene/Ge substrate by molecular beam epitaxy (MBE) is systematically investigated. Growth models for InAs NWs and parasitic islands on graphene/Ge are developed. Through rational design of growth parameters, the self-catalyzed growth of defect-free InAs NWs on graphene surfaces is ultimately achieved. Our experimental results indicate that lower growth temperature can effectively suppress the formation of stacking-fault defects in InAs NWs, no visible stacking-fault defects are observed in the samples grown below 510 degrees C, and the intrinsic mechanism for this is clarified with the density functional theory (DFT) calculations.

HgTe quantum wells (QWs) with inverted band structures and strong spin-orbit coupling provide a versatile platform for studying topological quantum transport. Quantum Hall scaling near plateau-plateau transitions provides a sensitive probe of the crossover between localized and extended states. Here we investigate plateau-plateau transitions in a 23 nm-wide HgTe QW with a reduced effective energy gap, where macroscopic transport is not strictly limited to a single effective two-dimensional channel. By analyzing the temperature- and illumination-dependent maximum Hall slope, we extract the scaling exponent kappa, which is treated here as an effective scaling exponent derived from macroscopic transport, and identify a pronounced temperature-driven crossover. At low temperatures, kappa deviates from commonly reported values and evolves toward the range typically observed in conventional two-dimensional systems at elevated temperatures, while Landau-level quantization remains clearly identifiable. Infrared illumination further modifies the extracted kappa and shifts the crossover toward lower temperatures, reflecting an effective modulation of the transport response. These results show that quantum Hall scaling in wide HgTe QWs is influenced by the interplay between disorder-related dissipative transport and finite phase coherence, highlighting the applicability and limitations of scaling analysis beyond the single effective two-dimensional channel regime.

The self-catalyzed growth of InAs nanowires (NWs) on graphene is achievable but typically yields short, thick NWs with frequent stacking-fault defects. In this work, we demonstrate the successful synthesis of defect-free, ultralong InAs NWs by harnessing the synergistic effects of graphene and an Au catalyst. The distinct roles of graphene and Au in promoting the growth of high-quality NWs were systematically elucidated. Atomic resolution scanning transmission electron microscopy (STEM) imaging revealed that the Au-catalyzed InAs NWs grown on graphene predominantly exhibit defect-free wurtzite structures, whereas a small portion of nanosheets and the NWs grown atop them display defect-free zinc blende phases. Based on these observations, a growth model for Au-catalyzed InAs NWs on defective graphene/Ge surfaces was proposed.

Charge-sensitive infrared phototransistors (CSIPs) based on GaAs/AlGaAs double quantum well structures have emerged as promising detectors for the scattering type scanning near-field optical microscope (SNOM), owing to their exceptional sensitivity in infrared radiation detection. These devices enable real-space mapping of nanoscale thermal phenomena, including thermal electron energy dissipation. However, the performance of CSIP still requires further optimization to detect extremely weak near-field signals, enabling higher temporal and spatial resolution in SNOM. In this work, we have demonstrated a GaAs/AlGaAs CSIP with significantly enhanced optoelectronic performance, achieved through oxygen impurity concentration reduction and implementation of a modulation doping scheme to boost the two-dimensional electron gas mobility in the lower quantum well. The optimized device exhibits a photocurrent of 7.43μA under a source-drain bias of 30 mV at 4.2 K, achieving an exceptional responsivity of 1.34 × 106A W-1at a radiation power of 5.54 pW. Notably, the devices maintain a well-defined peak response wavelength at 11.78μm and remain operational at temperatures up to 50 K. These advancements significantly enhance the detection capability of CSIPs for near-field thermal imaging applications.

Hybrid light-matter quasiparticles, or polaritons, are foundational to next-generation photonic and quantum technologies; however, their practical application is strictly limited by a fundamental trade-off between interaction strength and optical loss. Here, we overcome this limitation using a scalable semiconductor platform that achieves ultrastrong coupling (USC) between surface plasmons and lattice phonons with exceptional coherence. By fabricating epsilon-near-zero (ENZ) nanocavities directly into high-quality crystalline III-V semiconductors, we preserve the material's intrinsic long-range atomic order, enabling a pristine phononic response. This "crystal advantage" yields a normalized coupling strength (g/omega 0) of up to 0.28 and a cooperativity (2g/gamma avg) exceeding 14-a 7-fold improvement over previous systems based on disordered materials. Our top-down fabrication approach compresses the optical mode volume by 5 orders of magnitude below the diffraction limit while remaining compatible with mature 80 nm-node semiconductor manufacturing processes. Furthermore, we demonstrate the platform's versatility by realizing the simultaneous ultrastrong coupling of a single plasmon mode to multiple distinct phonon modes within a semiconductor heterostructure. This work establishes a new paradigm for low-loss on-chip polaritonics, opening avenues for mass-producible terahertz devices and the exploration of many-body quantum phenomena.

High-performance multispectral infrared photodetectors are essential for advanced imaging and sensing technologies. Here, we demonstrate a frequency division multiplexed (FDM) dual-band infrared phototransistor operating at 9.9 and 14.9 mu m through a single source-drain channel. The device incorporates a double GaAs/AlGaAs quantum well (QW) structure, where two QWs of different thicknesses (7 and 11 nm) serve as charge-sensitive intersubband absorbers. Optical excitation at each wavelength induces opposite charge polarities on a floating gate, which are selectively demodulated by periodic resetting with distinct frequencies. This FDM operation enables simultaneous, independent readout of both spectral bands. Finally, we demonstrate absolute temperature sensing using the dual-band response, highlighting the device's potential for compact multispectral infrared sensing and imaging systems.

The optoelectronic properties of infrared detectors lie in the uniformity of semiconductor film materials. Effects of InP substrate roughness nonuniformity on the homogeneity of surface morphology, lattice structure, optical property and minority-carrier lifetime of wavelength extended InGaAs epitaxial material grown via molecular beam epitaxy (MBE) are investigated. Moreover, the direct correlation between epitaxial material nonuniformity and detector focal plane signal response is also assessed. Results show that under strict macroscopic control of growth parameters, slight nonuniformity of the substrate roughness will be amplified and cause a significant deterioration in the lattice quality, optical and electrical properties of epitaxial layers. The strong spatial correlation between the minority-carrier lifetime of the epilayer and the detector response nonuniformity underscores the critical, and previously underappreciated, role of substrate roughness uniformity in achieving high-performance lattice-mismatched infrared detectors.

Multiple indistinguishable quantum dots integrated within one photonic chip hold potential for quantum systems. We experimentally demonstrate a nonlocal metasurface enabling the tuning of distant GaAs quantum dots to one wavelength with enhanced free-space outcoupling.

Low-power and high-speed terahertz (THz) photonic devices are of significant importance for advancing THz technologies, demanding exceptional functional materials to load. In this work, we systematically investigate the transient charge transport dynamics in semimetallic mercury telluride (HgTe) films utilizing optical pump-THz probe (OPTP) spectroscopy. Remarkably, photoexcited bare HgTe exhibits an ultrasensitive transmission response in THz frequencies at room temperature-reaching a modulation depth of 28% at a mere pump fluence of 1 mu J/cm2 and up to 73% at 21 mu J/cm2-surpassing all reported materials under comparable conditions. Moreover, the photocarrier relaxation remains ultrafast and nearly constant (similar to 14.3 ps) across a wide range of pump fluences. Through detailed analysis of THz photoconductivity spectra, Drude-Smith model fitting, and temperature-dependent transient dynamics, we reveal that HgTe's superior performance stems from its semimetallic character, featuring ultrahigh electron mobility enabled by long momentum scattering times and a small effective mass, as well as its gapless electronic structure. Our findings provide deep insights into the photocarrier relaxation mechanism in HgTe and highlight its immense potential for developing energy-efficient, broadband, all-optically controlled, ultrafast THz modulators and other high-performance THz optoelectronic devices.

In the photoreflectance (PR) of semiconductor heterostructure layers, modulated signals may arise from the modulation of both surface and interface electric potentials. Effectively distinguishing these different sources is necessary to unravel the interfacial electronic properties. However, understanding this aspect remains a challenge for the PR technique. This work revisits the topic through PR experiments on the lattice-matched single heterostructure (SH) of InGaAs/InP and the double heterostructure (DH) of InP/InGaAs/InP, which were grown by molecular beam epitaxy. We examine the modulation effect at two laser wavelengths, 532 nm and 1064 nm, for which the 1064 nm laser only generates modulation of the interface electric field for the DH sample. The confined energy levels of a two-dimensional electron gas at the interface are disclosed under the modulation of either laser. However, the 1064 nm laser is beneficial to probe the interface electronic structure of the deeply buried interface, avoiding the inhibition from the absorption of the InP layer on top. Furthermore, the results of the DH sample with the modulation of the 1064 nm laser demonstrate the other virtue of the interface modulation: it allows probing of the wide bandgap semiconductor, despite the laser having lower energy than that demanded to excite the band-to-band transition of the wide energy bandgap.

Bipolar photoresponse - where photocurrent polarity reverses with excitation wavelength, gate voltage, or other conditions - is essential for optical logic, neuromorphic computing, and imaging. Unlike unipolar responses, bipolar behavior enables direct binary encoding and enhanced photodetection contrast. However, in conventional photoconductive or photovoltaic systems, the simultaneous and opposite-directional transport of electrons and holes often suppresses polarity switching. Recent self-powered Shockley-Ramo (SR) photoresponse in gapless materials also show only unipolar signals due to strong, irreversible electron-hole asymmetry. Here, we demonstrate for the first-time bipolar SR photoresponse in GaAs nanoconstriction devices by exploiting reversible electron-hole asymmetry. The longer carrier lifetimes in GaAs enable sub-diffusion-length control of carrier dynamics through geometry. By tuning photocarrier dynamics near the nanoconstriction for both majority electrons and minority holes, we modulate the SR response to exhibit dual polarities. At low excitation, photoelectrons dominate; as excitation increases, intervalley scattering populates higher-energy L-valleys, reducing electron contribution and leading to polarity reversal driven by the growing dominance of photoexcited holes. These results, supported by SR theory, show that nanoscale geometric engineering, together with the reversible electron-hole asymmetry, enables self-powered bipolar photocurrent responses, offering new routes toward advanced optoelectronic devices.

InGaAs nanowires (NWs) show exceptional potential in near-infrared photodetection due to their excellent optoelectronic properties. However, the high intrinsic carrier concentration of the InGaAs NW and the ionization scattering caused by surface defect states result in a high dark current, which degrades the photodetection performance. Here, we prepared an InGaAs NW field-effect transistor modulated by ferroelectric polymer P(VDF-TrFE), where the non-volatile ultra-high electrostatic field from polarization of the P(VDF-TrFE) film modulates the carrier distribution and energy band structure inside the NW. When the P(VDF-TrFE) film is in a negative polarization state, the electrostatic field depletes the carriers in the NW channel, remarkably suppressing the dark current by over two orders of magnitude. Consequently, our single InGaAs NW photodetector achieves both remarkable responsivity (R) of 1.1 x 103 A W(-1 )and specific detectivity (D*) of 7.5 x 10(12) Jones at the optical communication wavelength, significantly exceeding the commercial InGaAs and the nanowire-based photodetector. Moreover, the suppressed dark current enhances the polarization-sensitive detection capability, increasing the polarization ratio from 1.3 to 3.6. This enables the application of our device to polarization-sensitive infrared imaging. Our work demonstrates the value of ferroelectric polymer modulation for low-dimensional, high-performance infrared photodetectors.

Growth on patterned graphene/Ge provides a route to improve the film quality of large mismatch heteroepitaxy and simultaneously facilitate the transfer of epitaxial films; however, the growth process and its associated technical challenges remain unclear. In this work, the molecular beam epitaxy (MBE) growth of CdTe films on micro-scale patterned strip-like graphene/Ge (100), containing selective area epitaxy (SAE) of CdTe seeds on exposed Ge and the merging process of CdTe seeds, were systematically investigated. The effects of growth temperature on the SAE of CdTe seeds were studied in detail, and a growth model of the CdTe seeds was proposed. Additionally, we examined the morphology and crystal quality of CdTe films at different growth stages, identifying the suppression of CdTe nucleation on graphene during the CdTe seed growth and merging as a key challenge to obtain high-quality films on patterned graphene/Ge.

Perfect graphene substrates can improve the quality of films grown by large-mismatch heteroepitaxy and simultaneously enable the transfer of epitaxial layers. However, large-area chemical vapor deposition-grown graphene suitable for practical applications typically contains various defects, and the influence of these defects on heteroepitaxial growth remains unclear. In this work, we systematically investigated the molecular beam epitaxy growth of CdTe films on graphene/Ge substrates. The effects of graphene defects on the nucleation behavior and crystal structure of CdTe grains were elucidated, and epitaxial models for CdTe on three types of graphene/Ge surfaces were proposed. Furthermore, we evaluated the crystal quality of CdTe films grown on different graphene/Ge substrates and found that the quality of the epitaxial films is strongly correlated with the defects in graphene.

The wafer bow caused by lattice mismatch between metamorphic InGaAs epitaxial layer and InP substrate has become one of the key factors limiting the large-scale development of extended wavelength InGaAs focal plane array photodetectors. By introducing tensile strain in InAlAs buffer layers and InAlAs cap layer to compensate the compressive strain caused by lattice mismatch, the wafer bow was decreased from 55.9 mu m to 22.2 mu m. The influence of strain compensation structure on the anisotropy of metamorphic InGaAs materials was investigated by stress distribution, surface morphology, and PL uniformity. XRD and PL characterizations indicate that small tensile strain in InAlAs buffer layers did not reduce the quality of metamorphic InGaAs epitaxial material. This study shows that strain compensation is an effective method to control wafer bow and decrease anisotropy of metamorphic InGaAs materials grown on InP substrate.

Quantum light sources, particularly single-photon emitters (SPEs), are critical for quantum communications and computing. Among them, III-V semiconductor quantum dots (QDs) have demonstrated superior SPE metrics, including near-unity brightness, high photon purity, and indistinguishability, making them especially suitable for quantum applications. However, their overall quantum efficiency—determined by a product of the internal, excitation, and outcoupling efficiencies—remains limited, primarily due to low (typically below 0.1