For low-light and high-resolution spectral applications, intensified scientific CMOS(IsCMOS) are often adopted to improve signal-to-noise ratio, but their influence on system performance has not been systematically characterized, making it difficult to ensure design-level performance. In this work, we propose a combined optical-algorithmic approach to ensure both resolution and throughput in ultraviolet spectroscopy. A freeform Czerny-Turner spectrometer incorporating an IsCMOS detector was designed and implemented, achieving a target resolution of 0.1 nm across the 250-310 nm range. By replacing spherical mirrors with freeform reflective surfaces, the numerical aperture was increased by 3.2x, significantly enhancing light collection efficiency while maintaining the designed resolution. However, experimental measurements revealed that the IsCMOS introduced spectral broadening and peak drift. And these degradations were strongly gain-dependent and were attributed to variations in electron trajectories at the microchannel plate output. To address this issue, a non-blind deconvolution method was applied to compensate for the spectral broadening and drift, successfully restoring the system resolution to 0.1 nm across the full spectral range. This study, for the first time, systematically characterizes the gain-dependent effects of IsCMOS, providing new insights and guidance for the calibration of precision ultraviolet spectrometers.

Quantum key distribution (QKD) is a pivotal quantum communication technology but faces practical challenges such as transmission loss and measurement device vulnerabilities. Mode-pairing QKD (MP-QKD) addresses these limitations by dynamically pairing single-photon detection events, enabling secure long-distance communication with simplified experimental requirements. However, optimizing key parameters like pulse intensity remains computationally demanding for traditional numerical methods. To overcome this, this paper shows a machine learning framework that combines Particle swarm optimization (PSO) and three neural networks—Backpropagation neural network (BPNN), XGBoost, and Long short-term memory (LSTM)—to predict optimal pulse intensity under varying environmental conditions. Using PSO-generated datasets, the models map channel loss, error rates, transmission distance, and other parameters to pulse intensity. Simulations demonstrate that BPNN achieves 99.87% prediction accuracy (RMSE: 0.0026) with an average runtime of 13 milliseconds per prediction, outperforming XGBoost and LSTM in both speed and precision. This work establishes a scalable solution for real-time parameter optimization in large-scale QKD networks and highlights the transformative role of machine learning in advancing quantum communication technologies.

beta-Ga2O3 as the next generation ultra-wide bandgap semiconductor has been widely used to fabricate solar blind photodetectors and high-voltage power devices. However, due to the self-doping induced intrinsic n-type characteristic of /3-Ga2O3, up to now, the researchers usually have to employ some other p-type semiconductors to fabricate the /3-Ga2O3 based p-n heterojunction devices. The lack of p-type /3-Ga2O3 severely restricts the development of /3-Ga2O3 based optoelectronic devices for enhanced performances. Here, we achieved controllable p-type doping of /3-Ga2O3 thin films using nitrogen-doping through ammoniation engineering. The p-type characteristic of the ammoniated film was confirmed by the Hall measurements, and the carrier concentration and mobility reach up to 5.43 x 1017 cm-3 and 16.82 cm2V- 1s- 1, respectively. Remarkably, the p-type /3-Ga2O3 film is rather stable against high temperature and shows long term stability, which makes it an excellent candidate for ex-situ growth of homo- or heterojunctions and following device integrations. To demonstrate this, a self-powered photodetector fabricated by /3-Ga2O3 p-n homojunction was constructed, which exhibits a large on/off ratio of more than 104 and a responsivity of 28.1 mA/W at zero bias, demonstrating superior performance than other /3-Ga2O3 based heterojunction photodetectors. Our results not only prove the feasibility of achieving ptype /3-Ga2O3 films, but also provide a guidance for obtaining other p-type semiconducting materials.

Oxygen vacancies (Vo) can significantly degrade the electrical properties of indium oxide (In2O3) thin films, thus limiting their application in the field of ultraviolet detection. In this work, the Vo is effectively suppressed by adjusting the Trimethylindium (TMIn) flow rate (fTMIn). In addition, with the reduction of the fTMIn, the background carrier concentration and the roughness of the film decrease gradually. And a smooth In2O3 thin film with roughness of 0.44 nm is obtained when the fTMIn is 5 sccm. The MSM photodetectors (PDs) are constructed based on In2O3 thin films with different fTMIn to investigate the opto-electric characteristics of the films. The dark current of the PDs is significantly reduced by five orders from 100 mA to 0.28 μA with the reduction of the fTMIn from 50 sccm to 5 sccm. In addition, the photo response capacity of PDs is dramatically enhanced. The photo-to-dark current ratio (PDCR) increases from 0 to 2589. Finally, the PD with the fTMIn of 5 sccm possesses a record-high responsivity of 2.53 × 103 AW−1, a high detectivity of 5.43 × 107 Jones and a high EQE of 9383 × 100%. Our work provides an important reference for the fabrication of high-sensitivity UV PDs.

Dual-color photodetection can increase detection accuracy due to the specific information from different wavelengths. Traditional dual-color detectors are based on double optical modules or photovoltage devices, which suffer from huge system weight or low gain. In this Letter, a novel dual-color photodetector with Ge/Graphene/CdS sandwich profile is proposed. While visible and infrared light is mainly absorbed by the CdS and Ge layers, respectively, photoelectrical signals from two wavelengths both conducted by graphene are extracted on time-sequence with different sampling frequencies. Based on a tailored interface process and epitaxy InGaAs instead of bulk Ge layer, the difference in response speed more than 3 orders of magnitude (76 kHz/14 Hz) was realized. Due to the photogating effect, the high gain was obtained for both wavelengths, and a photoresponse enhancement originated from the overlapping of local photogating field is observed. The device provided a new solution for high-gain and CMOS-compatible dual-color photodetection.

Surface texturing has been demonstrated to be very effective in improving the extraction efficiency of light emitting diodes (LEDs). In this paper, high-brightness AlGaInP-based vertical LEDs (VLEDs) with nanoscale silicon oxide (SiO2) hemisphere array were successfully fabricated by photoresist thermal reflux technique and laser interference exposure. It is the first time to combine interferential lithography and thermal reflux technique to make a regular nanoscale hemisphere array to enhance LEE for LEDs Compared to LEDs with microscale SiO2 hemisphere array, with planar SiO2 and without SiO2, electroluminescent measurements show that four LEDs have a similar threshold voltage. Simultaneously, the light output power (LOP) of LEDs with nanoscale and microscale SiO2 hemisphere array has been improved up to 40% and 20% at 200 mA, respectively, in comparison to LEDs without SiO2. It fits the simulated results well, which were obtained by the finite-difference time-domain (FDTD) method. Furthermore, it is demonstrated that more light emits out in the direction perpendicular to the epitaxial wafer by angle-resolved EL spectra for LEDs with nanoscale SiO2 hemisphere array, which accords to the simulated optical field distribution images. This kind of high-brightness LEDs with nanoscale SiO2 hemisphere array will have promising applications in meeting different requirements in special situations, such as headlights, flashlights. The new method is capable of fabricating large-scale nanostructured materials with good controllability and low cost, which will be widely used in improving properties of all kinds of LEDs, especially Mini LEDs and Micro LEDs.

A detailed geometric model for calculating the edge dislocation density through X-ray diffraction rocking curves is proposed in this study. Based on this model, we deduce a new formula to evaluate the edge dislocation density from the full-width at half-maximum values of skew symmetric rocking curves. The widely used formula proposed by Srikant et al. is an approximate result of this formula. The fitting results obtained by the two formulae coincide well from the measurement data of gallium nitride films grown on silicon substrate.

In this paper, a virtual GeSi template has been successfully fabricated by Ge filling the porous silicon (PSi) prepared by electrochemical etching (EC etching). The microstructure quality measured with cross-sectional scanning electron microscopy and photoluminescence spectra reveal that the PSi structure is fully filled with uniformly distributed Ge. Furthermore, Raman and X-ray diffraction results also show that the template has a typical GeSi feature, which originates from Ge interdiffusion with PSi during the Ge deposition. This design and structure can be expected to be useful as a template for Ge-related materials growth and device fabrication.

We demonstrate that a low-temperature GaN insertion layer could significantly improve the surface morphology of non-polar a-plane GaN.The two key factors in improving the surface morphology of non-polar a-plane GaN are growth temperature and growth time of the GaN insertion layer.The root-mean-square roughness of a-plane GaN is reduced by 75％ compared to the sample without the GaN insertion layer.Meanwhile,the GaN insertion layer is also beneficial for improving crystal quality.This work provides a simple and effective method to improve the surface morphology of non-polar a-plane GaN.

We present a method to extend the operating wavelength of the interband transition quantum well photodetector from an extended short-wavelength infrared region to a middle-wavelength infrared region. In the modified InAsSb quantum well, GaSb is replaced with AlSb/AlGaSb, the valence band of the barrier material is lowered, the first restricted energy level is higher than the valence band of the barrier material, the energy band structure forms type-II structure. The photocurrent spectrum manifest that the fabricated photodetector exhibits a response range from 1.9 μm to 3.2 μm with two peaks at 2.18 μm and 3.03 μm at 78K.

Hexagonal boron nitride (hBN) supports two types of hyperbolic phonon polaritons (HPPs), whose properties of strong electromagnetic field confinement and low propagation loss have been proposed for various applications in nanophotonics. Conventionally, real-space imaging of HPPs by scattering-type scanning near-field optical microscopy (s-SNOM) with vertical polarization excitation contains both tip and edge launched polariton modes, which leads to hybrid interference fringes. In this work, we symmetrically study the tip and edge excited HPPs in both boron nitride with the natural distribution of boron isotopes (natural hBN) and 11B isotope-enriched boron nitride (99.2% 11B hBN). The intrinsic HPPs excited in 99.2% 11B hBN exhibit a lower damping rate and longer propagation length than that in natural hBN. We experimentally realize a tuning from tip-dominated to edge-dominated excited HPPs by rotating the polarization of incident light. The near-field electric field intensity (NEFI) of edge-excited HPPs Eedge and the angle β (between the hBN edge and the projective direction of the incident electric field on the hBN plane) present a sine function relationship as Eedge ∝ |sin β| under an s-polarized incident light. The NEFI of edge-excited HPPs in 99.2% 11B hBN shows a 10% enhancement compared to natural hBN under the same measurement conditions. Our findings demonstrate an effective approach to reducing phonon polariton damping and manipulating phonon polariton excitation in hBN, which are beneficial for developing HPPs-based nanophotonic applications.

The interface, optical and electrical properties of InGaN light emitting diodes (LEDs) with different H2 flow treatment during the barrier growth are investigated in this study. With H2 treatment, the interface between the quantum well and barrier becomes rougher and the photoluminescence intensity decreases. The external quantum efficiency of the LEDs with 600 sccm (2.7%) H2 treatment has the best performance among the samples. Both the forward and reverse leakage currents of the samples are reduced significantly when treated with H2. Among the samples, a H2 flow with 600 sccm (2.7%) gives the best performance.

Relevant experiments have shown that more than 90% of photo-generated carriers can escape from multiple quantum wells (MQWs) sandwiched between p-type and n-type layers (a PIN structure). The escape time of the photo-generated carriers is on the femtosecond scale, much less than their relaxation time. In contrast, photo-generated carriers cannot escape from MQWs sandwiched between two n-type layers (a NIN structure) with bias. We found that there is a high barrier for holes and that the electric field intensity in QWs is close to zero, resulting in holes accumulating and a low escape efficiency in a NIN structure with bias.

The influence of excessive H-2 flow during barrier growth on optical and electrical properties of InGaN light-emitting diodes (LEDs) are investigated in this study. The room temperature photoluminescence of LEDs decays with excessive H-2 treatment. Temperature-dependent photoluminescence (TDPL) reveals an increase of the density and a decrease of the activation energy of deep non-radiative recombination centers in the H-2 treated LEDs. The external quantum efficiency (EQE) of the LEDs suffers from excessive H-2 treatment. The leakage current on the reverse and forward sides of the LEDs are reduced significantly when treated with H-2, which may be due to the suppressed Poole-Frenkel effect.

An internal photoemission-based silicon photodetector detects light below the silicon bandgap at room temperature and can exhibit spectrally broad behavior, making it potentially suited to meet the need for a near-infrared pure Si photodetector. In this work, the implementation of a thin Au insertion layer into an ITO/n-Si Schottky photodetector can profoundly affect the barrier height and significantly improve the device performance. By fabricating a nanoscale thin Au layer and an ITO electrode on a silicon substrate, we achieve a well-behaved ITO/Au/n-Si Schottky diode with a record dark current density of 3.7 × 10 − 7 A / cm 2 at − 1 V and a high rectification ratio of 1.5 × 10 8 at ± 1 V . Furthermore, the responsivity has been obviously improved without sacrificing the dark current performance of the device by decreasing the Au thickness. Such a silicon-based photodetector with an enhanced performance could be a promising strategy for the realization of a monolithic integrated pure silicon photodetector in optical communication.

Nonpolar (11–20) a-plane GaN films with AlN nucleation layer were grown on (10–12) r-plane sapphire substrate by metal organic chemical vapor deposition (MOCVD). The crystalline and surface qualities of a-plane GaN were found to closely depend on the growth conditions of AlN nucleation layer. With decreasing AlN growth temperature, the AlN grains became larger and sparser, which significantly reduced the defects density of a-plane GaN films. The growth time of the low temperature AlN layer was further optimized, and a-plane GaN films with reduced anisotropy in the crystalline quality, surface morphology and in-plane strains were achieved. It was found that the lateral growth lengths along different directions of GaN could be modulated by the growth time of AlN nucleation layer, thus changing the anisotropy of a-plane GaN films.

We propose a new method for fabricating large-scale uniform high-quality submicron inverted pyramid pit arrays by laser interference lithography (LIL), combined with dry etching and wet etching. In this process, uniform photoresist dot arrays are fabricated by LIL for 2-inch wafer. Dry etching is used to ensure the formation of the fluorocarbon organic polymer (FOP) mask layer. Wet etching parameters are investigated in details and inverted pyramid pits with {111} sidewalls are formed by anisotropic wet etching. Using this method, we have successfully produced uniform high-quality inverted pyramid pit arrays with the average size of 240 nm and the period of 450 nm. The size of pits can be tailored between 200 nm and 400 nm and the size deviation of inverted pyramid pits is 6.7% over the whole 2-inch wafer. This method offers a simple, less time consuming and cost-effective process of micro-nano pattern fabrication. Besides, GeSi QDs are quantitatively investigated by a nucleation model which shows GeSi QDs are preferentially grown at the tip of inverted pyramid pit and four intersection lines of two {111} planes inside the pit.

Achieving efficient ultralong purely organic phosphorescent luminophores is still a big challenge due to the slow intersystem crossing (ISC) process. Herein, we present a facile molecular design strategy that incorporates a secondary group (Br atom or methoxy group) into o-BrCz that can significantly enhance the ISC rate constant (kISC) and achieve high phosphorescence quantum yields (ΦP). As a result, DBrCz and MeBrCz achieved a profound increase of kISC ≈ 108 s-1 and obtained excellent ΦP values up to 24.53 and 27.81% in solid powder, respectively. Given the highly efficient ΦP and proper τp, DBrCz and MeBrCz are applied to alternating current (AC) light-emitting diodes (LEDs), achieving a white LED with CIE coordinates (0.28, 0.29) and a CRI over 90. As a proof of concept, we demonstrate its compensation effect on the dark duration of AC-LED with a reduced percent flicker of 78%. This result extends a new potential application for RTP luminophores in the lighting field.

Utilizing the high efficiency of the localized carrier extraction in the low-dimensional semiconductors within a PN junction, an InP-based InAs/InGaAs/InAlAs interband quantum well infrared photodetector has been investigated. Although the thermal energy is much less than the band offset, the detector still realizes photo response up to 1.93 mu m. In addition, the detector shows the room-temperature external quantum efficiency of 7% and detectivity of 1.81 x 10(10) cm root HZ/W without anti-reflection layer. Based on the above quantum efficiency value, an absorption coefficient of 1.1 x 10(4) cm(-1) was also determined. It is clear that our work provides compelling evidences for the possibility of novel and low-cost infrared photodetector. (C) 2019 The Japan Society of Applied Physics

Heterojunction phototransistors（HPTs）with scaling emitters have a higher optical gain compared to HPTs with normal emitters.However,to quantitativel.y describe the relationship between the emitter-absorber area ratio（A e /A a ）and the performance of HPTs,and to find the optimum value of A e /A a for the geometric structure design,we develop an analytical model for the optical gain of HPTs.Moreover,five devices with different A e /A a are fabricated to verify the numerical analysis result.As is expected,the measurement result is in good agreement with the analysis model,both of them confirmed that devices with a smaller A e /A a exhibit higher optical gain.The device with area ratio of 0.0625 has the highest optical gain,which is two orders of magnitude larger than that of the device with area ratio of 1 at 3 V.However,the dark current of the device with the area ratio of 0.0625 is forty times higher than that of the device with the area ratio of 1.By calculating the signal-to-noise ratios（SNRs） of the devices,the optimal value of Ae/Aa can be obtained to be 0.16.The device with the area ratio of0.16 has the maximum SNR.This result can be used for future design principles for high performance HPTs.