In this study, we proposed a crystalline SiN-capped AlGaN/GaN high electron mobility transistor (HEMT) with an AlN sub-cap layer. Based on geometric phase analysis, the introduction of an AlN sub-cap layer mitigates the strain at the SiN/AlGaN interface, leading to a more uniform strain distribution and high-quality interface characteristics with low interface state density. Compared with the devices without a sub-cap layer or with a gallium nitride (GaN) sub-cap layer, the GaN HEMTs with an AlN sub-cap layer exhibit lower on-resistance and higher electron mobility. Additionally, the devices show an enhanced threshold-voltage stability characterized by the thermal stimulation (ΔVth = −0.05 V at 25 and 150 °C) and the gate-bias stress (ΔVth = 0.02 V during the 1000 s at VGS = 2 V). The high-performance crystalline SiN-capped GaN HEMT with an AlN sub-cap layer demonstrates great potential for the high-reliability power transistors.
Existing methods are often limited by their underlying physical models, making it challenging to achieve single-shot, non-invasive multispectral imaging through scattering media. In this Letter, a speckle correlation model for the single-shot imaging of multispectral targets is developed. By using a gradient descent method based on differentiable computation, efficient multispectral imaging through scattering media is achieved. The method requires no additional system modulation and uses only minimal computational resources for fast reconstruction. Reconstruction results obtained by conventional methods and by the proposed method are compared under increasing spectral differences. Additionally, the proposed method can image hidden targets with spectral differences of up to 160 nm.
The potential energy surface (PES) fundamentally governs the motion of mobile ions in superionic conductors (SICs). In particular, flat local PES around mobile ion sites, indicative of low vibration frequencies and soft lattice dynamics, are strongly associated with reduced migration barriers and fast ion transport. However, a fast and quantitative method for evaluating local PES flatness remains lacking. Here, we combine the bond valence site energy method with isosurface analysis and harmonic vibration analysis to quantify local PES flatness through two complementary descriptors: the isosurface-enclosed volume (Viso; geometric perspective) and the site-specific vibration frequency (νsite; dynamical perspective), and unveiling their hidden effects on ion transport. Analysis of representative SICs reveals that large Viso (0.019–0.084 Å3) and low νsite (2.304–5.069 THz) at specific mobile ion sites are characteristic of fast ion transport, whereas non-SICs consistently exhibit smaller Viso (0.002–0.009 Å3) and higher νsite (8.465–12.872 THz). The proposed thresholds of Viso = 0.01 Å3 and νsite = 7 THz show a clear separation between known SICs and non-SICs in the current dataset and are expected to serve as practical criteria for future high-throughput screening of new SICs.
The mechanical response of materials subjected to extreme conditions is governed by deformation mechanisms that can differ substantially from those operating under conventional loading. Using tin as a model system, we investigate deformation behavior at strain rates exceeding 106 s−1 and homologous temperatures above 0.80 Tm. Under these conditions, we observe a regime in which strength increases with temperature, consistent with deformation controlled by phonon drag. However, this anomalous “hotter-is-stronger” behavior is found to have an upper limit determined by the onset of impact-induced melting caused by adiabatic heating. For a given test temperature, melting initiates once the strain rate exceeds a critical threshold, leading to the formation of a liquid phase that softens the material response. In our experiments, the development of liquid is accompanied by material ejection, which further reduces the measured hardness. Beyond the onset of melting, the material exhibits conventional thermomechanical behavior, with strength decreasing as temperature increases. These findings establish the limits of phonon-drag-dominated deformation at extreme strain rates and temperatures and demonstrate the critical role of adiabatic melting in governing the transition between strengthening and softening regimes.
On-chip integrated thulium (Tm)-doped lasers operating at 1.6–2.4 μm are strategically positioned for biomedical, industrial, and remote-sensing applications, yet their realization on thin-film lithium niobate (TFLN) remains hindered by fabrication-induced optical losses. Here, we demonstrate the first integrated Tm-doped TFLN microring laser, fabricated via a photolithography-assisted chemo-mechanical etching technique. The 1.7 mm-circumference racetrack resonator achieves an intrinsic quality factor Q > 105. Under optical pumping at 785 nm, the Tm-doped TFLN microring resonator generates multi-mode lasing at ∼1.8 μm with a linewidth of 38.1 pm. The lasing threshold is measured to be 5.8 mW, with a wavelength tunability of −8.7 pm/mW. This work overcomes a key materials-processing bottleneck and establishes a viable pathway toward high-performance, 2 μm-band photonic integrated circuits.
We report on the frequency-dependent terahertz (THz) photoresponse of quantum point contacts (QPCs) operating in the tunneling regime. Although the high-frequency response of QPCs is often attributed to photon-assisted transport, our spectroscopic study across the 0.15–0.7 THz range reveals a complex resonant structure consisting of numerous conductance peaks that are inconsistently sensitive to polarization. We demonstrate that these resonances are independent of the QPC barrier potential but are instead determined by the device geometry. Numerical simulations confirm that these features arise from the excitation of 2D plasmon modes in the surrounding high-mobility two-dimensional electron gas. These resonant plasmonic effects inevitably modulate the QPC response, masking the intrinsic transport physics. Finally, we propose a strategy to isolate the fundamental QPC photoresponse by utilizing lower-mobility—on the order of 104 cm/V s—heterostructures to suppress plasmonic interference, providing a path toward validating theoretical models of high-frequency mesoscopic transport.
Native oxide formation (NbOx) at the niobium (Nb) metal–air interface is a source of microwave loss and performance variability in superconducting resonators. We introduce vapor-phase hexamethyldisilazane (HMDS) as a dry surface passivation treatment compatible with standard nanofabrication workflows. In five independent fabrication runs, HMDS-passivated resonators consistently demonstrate improved internal quality factor (Qi) and narrower performance distribution relative to paired unpassivated controls. The Qi improvement occurs across the full microwave power range, suggesting NbOx suppression as a contributing mechanism. Statistical depth profile analysis of Nb oxidation state by electron energy loss spectroscopy corroborates this mechanism, revealing smaller chemical shifts and shallower oxidation depth in passivated specimens relative to the control. Furthermore, re-measurement after 60 days of ambient storage shows that HMDS-passivated resonators retain their Qi, indicating their ambient stability. These results establish vapor-phase HMDS as a surface passivation strategy with strong potential for superconducting quantum devices.
We report the persistence of the converse piezoelectric effect to exceptionally high temperatures in ferroelectric congruent LiTaO3 single crystals. Resonant piezoelectric spectroscopy reveals a strong and stable piezoelectric response up to temperatures approaching the ferroelectric transition (Tc = 855 K), demonstrating remarkable thermal stability of the piezoelectric response. A finite electromechanical response persists up to the highest measurement temperature of 1050 K, whereas a pronounced enhancement develops below 915 K along the c-axis but is absent along the perpendicular direction. This anisotropic precursor enhancement develops in the absence of significant bulk elastic softening above Tc, distinguishing LiTaO3 from ferroelastic perovskites in which precursor behavior is accompanied by pronounced elastic anomalies. These observations demonstrate that coherent polar precursor behavior can persist to exceptionally high temperatures in a non-ferroelastic ferroelectric, considerably extending the experimentally established temperature range over which such behavior has been identified.
Mercury vacancies are among the most abundant native defects in HgCdTe alloys and have been considered to be a significant source of carrier recombination in these materials. The vacancies have been suggested to induce deep levels in the bandgap, which would explain the degraded minority carrier lifetimes observed in vacancy-doped materials. However, experimental techniques are unable to explicitly reveal the chemical identity of trap levels. In this work, we use first-principles methods to study the role of VHg in nonradiative capture in HgCdTe. We apply hybrid density functionals to calculate the evolution of the charge transition levels of VHg as a function of the alloy composition. Our results confirm a near mid-gap level induced by the vacancy in materials with cadmium molar fraction > 0.3. However, explicit calculation of the configuration coordinate diagram reveals extremely weak electron–phonon coupling associated with the mid-gap transition. Estimates of the upper limit of the capture cross sections indicate that the vacancies are unlikely to act as effective recombination centers. This study contributes to our understanding of the role that mercury vacancies play in these materials and redirects future efforts toward the mitigation of deep trap levels for the design of next-generation devices.
Halide solid electrolytes, exemplified by Li3YCl6 (LYC), offer moderate ionic conductivity (∼1 mS/cm), high oxidative stability (>4 V), and good mechanical deformability, making them promising candidates for solid-state lithium batteries. However, the room-temperature ionic conductivity of single-crystal LYC is nearly one order of magnitude higher than that of experimental polycrystalline samples. Grain boundaries (GBs) are considered the primary cause of this discrepancy. Although GBs critically influence Li-ion transport in most solid electrolytes, the impact in LYC remains poorly understood. Herein, we quantify the contribution of GBs to Li-ion transport in LYC utilizing machine learning driven deep potential molecular dynamics. For all GBs considered, the results reveal a strong inherent tendency toward polycrystallinity in LYC due to low GB formation energies. Although the ionic conductivity of all LYC GBs is lower than that of the bulk, among them, the highest activation energy and the lowest ionic conductivity are 0.246 eV and 8.6 mS/cm, respectively. Moreover, the {303¯2}⟨101¯3¯⟩ GB with the lowest GB energy (0.176 J/m2) exhibits the highest ionic conductivity of 13.9 mS/cm. The simulations demonstrate that GBs hinder overall Li-ion transport compared to the bulk, though GBs do not act as the dominant barrier to Li-ion transport in LYC. This work provides insights for the design of halide solid electrolytes.
Self-powered solar-blind ultraviolet (UV) photodetectors capable of operating at elevated temperatures are highly desirable for harsh environments, where power supply is limited and thermal reliability is critical. However, achieving self-powered operation, thermal stability, and sensitive solar-blind UV response simultaneously remains challenging. Diamond, with its ultrawide bandgap and excellent thermal and chemical stability, is a promising platform. Nevertheless, most diamond UV photodetectors still rely on external bias or complex heterojunctions, limiting their practicality. Here, we develop a boron-doped diamond platform for self-powered solar-blind UV photodetection at elevated temperatures. Under 225 nm illumination at room temperature, the device operates in a self-powered mode and delivers a photocurrent-to-dark current ratio (PDCR) of 105, a responsivity of 2.67 mA W−1, and a detectivity of 1.34 × 1013 Jones. Notably, at 300 °C, it still maintains a PDCR of 104, together with a responsivity of 18.8 mA W−1 and a detectivity of 1.48 × 1013 Jones. The device further exhibits good repeatability and stable operation at elevated temperatures, enabling demonstrations of high-temperature UV imaging and optical communication. These findings highlight diamond homojunctions as a viable platform for self-powered solar-blind UV photodetection at elevated temperatures, with potential for harsh-environment optoelectronic applications.
Layered oxides show great promise as cathode materials for sodium-ion batteries, attributed to their high theoretical specific capacity. Activating anionic redox reactions (ARR) is considered an effective strategy for further increasing the energy density. However, ARR is often accompanied by lattice oxygen loss and irreversible structural phase transformation. Herein, a honeycomb superstructure is constructed by introducing an appropriate amount of Mg at Mn sites within the transition metal (TM) layer of P2-Na0.72Li0.23Mn0.77O2. Thus, the collaborative regulation of lattice oxygen stability and phase structure stability is realized. First, upon Mg incorporation into the TM layer, a well-defined MgMn6 honeycomb superstructure is constructed. The honeycomb superstructure effectively suppresses phase transformation arising from Mn migration within the TM plane and simultaneously mitigates oxygen release associated with vacancy clustering. Second, the incorporation of Mg2+ with a larger ionic radius than Mn3+ and Mn4+ expands the interlayer spacing, thereby facilitating Na+ diffusion kinetics. Consequently, the as-optimized cathode achieves 86.5% capacity retention over 100 cycles at 1 C and 72.1 mAh g−1 at 5 C, demonstrating outstanding cyclability and rate capability. These findings provide a feasible modification strategy for improving anionic redox reversibility and energy density in layered oxide cathodes.
Zero-dimensional metal halides have attracted extensive attention as multifunctional optoelectronic materials and in radiation detection fields owing to their unique structural and luminescent properties. Herein, we take Sb3+-doped zero-dimensional hybrid zinc halide (C5H14N2)ZnCl4·H2O as the research object to systematically explore its crystal structure, carrier recombination kinetics, and exciton luminescence mechanisms. The results show that the introduction of Sb3+ can maintain the overall structural stability of the host lattice and significantly regulate the multi-channel radiative recombination pathways. This doped material displays characteristic dual-band luminescence with distinguishable carrier decay dynamics: the blue-green band originates from intrinsic band-edge self-trapped exciton recombination of the pristine matrix, whereas the near-infrared emission stems from characteristic inter-level carrier radiative transitions of Sb3+ dopants, accompanied by prolonged carrier lifetime and large Stokes shift. Temperature-dependent luminescence measurements uncover strong temperature dependence of the dual emission peaks in terms of carrier trapping/detrapping dynamics. The near-infrared luminescence presents prominent electron–phonon coupling, which reshapes carrier relaxation routes and induces an obvious spectral redshift. Density functional theory calculations further confirm that Sb3+ impurity introduces discrete mid-gap impurity states, enhances local orbital bonding interactions, and strengthens lattice rigidity and self-trapped exciton binding energy. These modifications optimize carrier localization, suppress non-radiative quenching channels, and ultimately facilitate efficient, stable radiative recombination of self-trapped excitons via regulated carrier transport and relaxation kinetics.
Plasmonic random lasers (PRLs) with unique photophysical properties have attracted considerable attention owing to their promising applications in speckle-free imaging, biomedical diagnosis, and optical sensing. In this work, low-threshold PRLs were realized by infiltrating a synthesized donor–acceptor–donor organic dye into a capillary fiber coated with silver nanoplates (AgNPs). For the capillary fiber without a silver nanoplate coating, several distinct narrow emission peaks emerged and underwent a slight blueshift with increasing pump fluence, owing to the band-filling effect. After coating the capillary fiber with AgNPs, more randomly distributed emission spikes with narrower linewidths were observed. In addition, the lasing threshold was significantly reduced to 0.86 mJ/cm2, which can be attributed to the combined effects of enhanced recurrent light scattering and localized surface plasmon resonance. The as-prepared PRL, characterized by its low spatial coherence, enables speckle-reduced imaging with significantly suppressed granular artifacts and a speckle contrast as low as 0.032.
Ultraviolet optoelectronic logic gates are attractive for low-power information processing in secure sensing and communication systems. Here, a self-powered, Ga2O3/GaN heterojunction photodetector (PD) that enables input-controlled reconfigurable ultraviolet (UV) optoelectronic logic gates under zero bias is reported. The built-in electric field of the heterojunction induces photocurrent polarity reversal under 254 and 365 nm illumination, providing the basis for logic-gate reconfiguration. On this basis, two operation modes, termed switch-to-logic (via LED on/off states) and voltage-to-logic (via driving-voltage modulation), are established to implement six representative Boolean logic functions including AND, OR, NAND, NOR, XOR, and XNOR with a single device. The photodetector exhibits zero-bias responsivities (R) of 1.8 mA/W at 254 nm and 1.23 mA/W at 365 nm, together with specific detectivities (D*) above 1×1010 Jones at both wavelengths. Logic switching is achieved by modulating either the illumination states or the driving-voltage windows of two UV light sources without altering the device structure. This work provides a compact and low-power proof-of-concept platform for self-powered UV optoelectronic logic gates and highlights the potential of wide-bandgap heterojunctions for low-power ultraviolet information processing.
A diode-pumped single-longitudinal-mode distributed Bragg reflector fiber laser operating at 1762 nm, corresponding to the electric quadrupole (E2) transition of barium ions, is demonstrated using a 2.5-cm-long 4 wt. % thulium (Tm3+)-doped germanate fiber. With the maximum available pump power of 270 mW at 793 nm, an output power of 7.24 mW was obtained with a slope efficiency of 21.7% with respect to the absorbed pump power without any active temperature control. Single-longitudinal-mode operation was verified using a scanning Fabry–Pérot interferometer. This compact single-longitudinal-mode fiber laser source represents a promising robust and reliable candidate for laser cooling and quantum computing applications, particularly for quantum systems based on barium ion traps.
Dye-doped optical microlasers are solid-state resonators made by mixing a laser dye into a polymer matrix. When optically excited, the dye fluorescence provides gain for laser modes. These modes are highly sensitive to changes in microlaser morphology. In this work, we study how gold nanoparticle (AuNP) surface coverage and magnetic field-induced deformation affect the transverse electric (TE) and transverse magnetic (TM) modes of a metal-hybrid whispering gallery mode (WGM) microlaser. The microlaser has a core–shell-like structure consisting of a Fe2NiO4/NBA 107 magnetic core, a Rhodamine 6G-doped NBA 107 gain layer, and a partially AuNP-decorated outer surface. A magnetic field induces deformation of the microlaser and modifies the effective optical path associated with the AuNP-decorated interface. Two optical paths are observed: a primary path along the full microlaser diameter and a secondary path associated with the AuNPs–microlaser interface. For ∼15% AuNP coverage, the primary FSR is 0.466 nm, while the second FSR changes from 0.652 nm at 1.2 mT to 0.597 nm at 3.6 mT before increasing to 0.614 nm at 4.8 mT. For ∼25% AuNP coverage, the primary FSR is 0.457 nm, and the second FSR appears at 0.515 nm at 1.2 mT before becoming perturbed at higher magnetic field. TE–TM mode splitting is observed for both AuNP coverage levels under applied magnetic field, with more frequent occurrences at higher fields and for the ∼25% AuNP coverage case. These results suggest that coupling magnetic field-induced deformation with a localized plasmonic nanoparticle interface can produce field- and coverage-dependent polarization mode splitting in hybrid WGM microlasers.
Extended states in localized continua (ELCs) are spatially extended modes embedded in spectra composed of localized states, forming the spatial inverse of bound states in the continuum (BICs). Here, we experimentally realize frequency-tunable higher-order ELCs in stacked non-Hermitian topolectrical circuits. In a bilayer quadrupole circuit, interlayer coupling splits higher-order corner states into frequency branches with opposite mirror parities and embeds each branch into the bulk band of the opposite-parity subspace without hybridization, yielding parity-protected higher-order topological BICs. With nonreciprocal coupling, the non-Hermitian skin effect (NHSE) reconstructs the bulk states into skin modes and delocalizes the embedded corner states into higher-order ELCs. We further extend this mechanism to a trilayer circuit, where three orthogonal interlayer eigenmodes with distinct parity-distribution characteristics produce three frequency-tunable corner states under interlayer coupling and generate richer spatial profiles of ELCs under the NHSE. This work establishes a stacking-enabled route for multifrequency control and tunable interlayer wave-function distributions of higher-order topological states.
Zirconium (Zr) is predicted and experimentally confirmed to substitute on the Al site (ZrAl), where it acts as a deep donor approximately 1.5 eV below the conduction band minimum in aluminum nitride (AlN). Furthermore, the neutral zirconium-nitrogen vacancy complex, (ZrAl–VN)0, has been predicted to be an attractive candidate for room-temperature qubits. In this work, Zr-doped AlN epilayers were synthesized on AlN bulk substrates via metal-organic chemical vapor deposition. Structural and morphological characterizations confirmed excellent crystalline orientation and sub-nanometer surface roughness. While photoluminescence spectra were dominated by vacancy-impurity complexes, photocurrent excitation spectroscopy effectively mapped Zr-related states. Specifically, an isolated donor level was resolved at 1.5 eV alongside (ZrAl–VN)0/1− complex configurations near 2 and 3 eV. Each complex exhibits a distinct 0.2 eV doublet splitting driven by π-bonding and σ-bonding configurations within the wurtzite lattice. These findings provide experimental confirmation of the deep-level electronic properties of Zr in AlN, establishing a framework for the development of extrinsic photoconductive semiconductor switches and room-temperature qubit applications.
