With the gradual saturation of the spectrum resources of radio frequency communication, there is an urgent need to open up a new race track for local highspeed communication, while visible light communication benefits from the nature of large bandwidth and spectrum licensefree since limited communication range, which is one of the ideal supplements of traditional communication. The rapid development of GaNbased bluegreen light source in the past decade, especially the development of microLED as the small size and high speed light source with excellent performance, has made it an important driving force for terminal communication in the "Internet of Everything" era of Internet of Things. In this paper, the development history and recent progress of bluegreen highspeed light sources are reviewed from two main categories: bluegreen microLED and GaNbased bluegreen light sources with resonators (including superluminescent diodes and lasers). It mainly includes three aspects: microLED structure and array, surface emitting cavity enhanced light source and edge emitting cavity enhanced light source.

AlGaN UV photodetectors and focal plane arrays, as allsolidstate devices, have intrinsic visible blind characteristics and can achieve solarblind detection without filters, thus they have become an important development trend for UV detection technology. In this paper, the developments and existing problems of AlGaN UV photodetectors and focal plane arrays are introduced. The development status and trends of AlGaN APD are also discussed.

βGa2O3 nanodot array films on intrinsic GaAs substrates have been presented by combining thermal oxidation and MOCVD technology, which does not involve metal catalysts or complex etching. Morphological features of the prepared films were characterized and analyzed by scanning electron microscope (SEM). It is found that the βGa2O3 nanodot array films show a pentagonal columnar structure. Xray diffraction, Raman vibration, and photoluminescence were performed on the prepared samples, and the results show that the crystal quality of the films is optimized with the increase of MOCVD growth temperature and Ⅵ/Ⅲ ratio. The finite element method (FEM) simulations verify that the βGa2O3 nanodot array films are highly light trapping. The nanodot array films prepared by this process show high specific surface area with high light trapping.

GaNbased microLED, as a burgeoning light source technology, has been demonstrated to play an important role in optical communication and display fields, etc. If the pixels in microLED array can detect the optical performance of the adjacent pixels, it is expected to realize multifunctional microLED array for monolithic integration with light detection, thus promoting the development of photonic integrated chips for Internet of Things technology toward miniaturization and low power consumption. It was experimentally verified that InGaN/GaN MQWs can realize the dual functions of luminescence and detection under different operating voltages, thus proving the feasibility of microLED array monolithic integrated luminescence and realtime detection. Moreover, microLED array was further applied in high stability visible light communication and realtime detection of dead pixels in display array, which broadens the potential applications of microLED array.

GaNbased UV laser diodes for nearUV wavelength (UVA LD, 320~400nm) are widely applied in the fields such as UV curing, 3D printing and medical. In this paper, the current status and key technical challenges of GaNbased UVA LD are reviewed, and then how to solve the main challenges of stress management, efficient ptype doping in AlGaN and minimizing polarization effect in multiquantum wells are analyzed from the epitaxial growth and structural design. This will provide theoretical guidance for the epitaxial growth of the GaNbased UVA LD with high power, low threshold and long life.

The Sidoped nonpolar aplane nAlGaN epitaxial layer with high electron concentration and good surface morphology was successfully grown on semipolar sapphire substrate by metal organic chemical vapor deposition. The effects of indium (In) surfactant and undoped AlGaN buffer layer on the structural and electrical properties of the nAlGaN epitaxial layer were intensively studied. The characterization results show that the anisotropy in crystalline quality of the nonpolar aplane nAlGaN epitaxial layer is effectively suppressed by using In surfactant and undoped AlGaN buffer layer, and its surface morphology and electrical properties are significantly improved. In fact, the electron concentration and electron mobility are determined to be -4.8×1017cm-3 and 3.42cm2/(V·s), respectively.

Metaloxidesemiconductor field effect transistor (MOSFET) devices based on wide bandgap (WBG) semiconductors such as gallium nitride (GaN) have a high electric field equivalent to the critical breakdown electric field of WBG semiconductor in the gate dielectric under the offstate voltage, which dampens the longterm reliability of the gate dielectric. In order to avoid using the immature ptype ion implantation technology in GaN devices, a new type of vertical GaNbased trench gate MOSFET based on selective area epitaxy is proposed, which can improve the gate dielectric reliability by reducing the offstate gate dielectric electric field. And a process preparation based on selective region epitaxy is designed to avoid the etching damage of MOS interface. The space charge competition model of the depletion region junction capacitance in the offstate is proposed, and the influence law and mechanism of the structural parameters of ptype shielding structure on the gate dielectric electric field are qualitatively explained. By trade off the relationship between device performance and reliability, a novel vertical GaNbased trench gate MOSFET with longterm reliability of gate dielectric is obtained with the breakdown voltage of 1200V and gate dielectric electric field of 0.8MV/cm.

Twodimensional diamond (2DD) is an atomically thick diamond film having unique characteristics with retaining intrinsic properties of bulk diamonds. Currently, researches on 2DD mainly focus on theoretical investigations of structure, functionalization, and electrical properties, while a few of experimental works are reported on preparation. In this paper, the theoretical and experimental progresses of structure, surface functional modulation and electrical properties of 2DD are briefly reviewed dependent on atomic thickness (layer number), and the development trends, challenges, and potential applications are discussed.

Hexagonal boron nitride (hBN) neutron detectors present such advantages as small leakage current, small volume, fast response speed, high detection efficiency and insensitivity to γrays, thus they are expected to be widely used as supplements of the traditional 3He gas detector and microstructure semiconductor neutron detector. The principles of hBN neutron detector are introduced in this paper, and the research progressed of hBN neutron detector in recent years are also reviewed, including the preparation process of hBN films, the structure and performance of hBN neutron detectors and so on.

With the wide applications of GaInP/GaAs/Ge threejunction solar cells used in spacecraft as a space power supply system, the problem of space radiation damage is widely concerned. The performance of GaInP/GaAs/Ge threejunction solar cells will be degraded by the irradiation of the electrons, protons and other radiation particles or rays in the space radiation environment. In this paper, the research progress of the radiation experiments of GaInP/GaAs/Ge triplet solar cells induced by the electrons, protons and other radiation particles or rays at home and abroad is introduced in depth, and then the research progress of the simulation of radiation damage effect, radiation hardening, and radiation damage prediction of GaInP/GaAs/Ge threejunction solar cells is reviewed. The key problems in the research of radiation damage effect on GaInP/GaAs/Ge threejunction solar cells are summarized. It provides theoretical guidance and experimental technical support for the establishment of the experimental method of radiation damage effect, the analysis of damage mechanism, the prediction of inorbit life and the research of radiation hardening technology of GaInP/GaAs/Ge threejunction solar cells.

A series of semipolar (1122) AlN epilayers have been grown on (1010) mplane sapphire substrates with the help of dual moderatetemperaturegrown (MTG) AlN interlayers by metalorganic chemical vapor deposition (MOCVD). Significant improvements in both surface morphology and crystalline quality of the semipolar (1122) AlN epilayers have been achieved with the insertion of the MTGAlN interlayers due to the formation of nanoscale patterned substratelike structure and the reduction in the basalplane stacking faults and their associated partial dislocations. The effect of the variation in the thickness of the MTGAlN interlayer ranged from 20 to 100nm was investigated in detail based on the characterization results of atomic force microscopy (AFM) and Xray diffraction. It was revealed that all the semipolar AlN epilayer samples were uniquely [1122]oriented regardless of the variation in the thickness of the MTG AlN interlayer. It was found that the most remarkable reduction in surface roughness and the most notable improvement in crystalline quality could be obtained when the thickness for the inserted dual MTGAlN interlayers was approximately 80nm.

For a Schottky detector with a thin absorption region of 100~200nm, the influence of different metal contacts on the dark current and spectral response characteristics was studied. Taking GaNbased materials as the main body, Au and Ni/Au were prepared on the surface of thin Al0.42Ga0.58N to form Schottky contacts, and Ti/Al/Ti/Au were prepared on the surface of Al0.55Ga0.45N to form ohmic contacts. Thus, an AlGaN Schottky solarblind detector with a thin absorption region is fabricated. The results show that for AlGaN material, the photoresponse of Au Schottky detector is good, reaching 0.10A/W, the peak external quantum efficiency is 47%, but the dark current is slightly larger, which is 3.91×10-10A/cm2. The dark current of Ni/Au Schottky detector is stable at 4.17×10-11A/cm2, while the responsivity is generally 0.07A/W, and the external quantum efficiency is 33%. The test results are consistent with the simulation model. For the front irradiation mode, Au Schottky detector has a larger response range and higher responsivity than Ni/Au Schottky detector due to factors such as barrier height and interface loss layer. For the back irradiation mode, the thickness of the absorption layer has a great effect on the response range, and the thin absorption region effectively extends the response range.

ScAlN thin films were first prepared on Si (100) substrate by pulsed DC magnetron sputtering. Then, GaN thin films were epitaxial grown on Si (100) substrate with metalorganic chemical vapor deposition (MOCVD) by using ScAlN as the buffer layer. The influence of the thickness of ScAlN buffer layer on ScAlN buffer layer and GaN epitaxial layer is investigated by high resolution Xray diffraction, atomic force microscopy (AFM) and Raman spectroscopy. The results show that the thickness of ScAlN buffer layer is an important factor affecting the crystal quality of GaN thin films. With the increase of ScAlN thickness, the full width at half maximum (FWHM) of ScAlN (002) Xray diffraction rocking curve continues to decrease, and the FWHM of GaN (002) Xray diffraction rocking curve first decreases and then increases. When the thickness of ScAlN buffer layer is 500nm, the crystal quality of GaN is the best, the FWHM of GaN (002) Xray diffraction rocking curve is 0.38°, and the tensile stress calculated by Raman spectrum is 398.38MPa.

GaNbased microsized lightemitting diodes (microLED) has gradually become the main light source in many optoelectronic devices such as visible light communications and nextgeneration displays. Low external quantum efficiency (EQE)，caused by nonradiative recombination and quantum confined Stark effect (QCSE)，is the main bottleneck in applications of microLEDs. In this report, the reasons for low EQE of microLEDs are discussed, and the physical characteristics of microLEDs are analyzed and several optimal methods are suggested to improve EQE.

In this article, first, the technical bottlenecks of ultraviolet lightemitting diodes (UV LEDs) encountered in the current stage of research and development are introduced. Then the inactivation mechanism of UV LEDs to harmful microorganisms in water is analyzed. In the process of microbial inactivation, the different application types of UV LEDs are examined in detail, including the application of UV LEDs in different types of UV reactors, advanced oxidation processes (AOPs) based on UV LEDs, the combined use of UV LEDs with different wavelengths, etc. Finally, the issues of deep UV LEDs in the field of drinking water sterilization and disinfection are summarized and an outlook is put forward.

Highperformance electronic devices with leadfree piezoelectric materials have been widely applied in various fields. Bismuthbased materials have certain comprehensive properties, especially in the field of high temperature piezoelectric, which is a candidate system with potential to replace PZTbased materials. In this paper, an overview of the research advances related to the key problem of how to modified the properties of leadfree piezoelectric materials is provided, focusing on the following aspects, such as the control of material components to modify the multiphase boundary, doping, adjustment of preparation process and domain engineering. In addition, this perspective tries to analyze the problems that still need to be solved in the practical applications of leadfree piezoelectric materials.

A kind of four spectral timedelayintegrated charge coupled device (TDI CCD) is designed and fabricated by integrating four TDICCDs on one chip. Different narrowband filter films are plated on the corresponding positions of the light window to realize multiband light splitting. For the designed TDICCD, its pixel size is 28μm×28μm, the horizontal pixel size is 3072 elements, the line frequency is 10kHz, the charge transfer efficiency is 0.99999, the saturation output voltage is 2650mV, the antiblooming ability is more than 100×, and the dynamic range is 7143∶1.

Distributed feedback (DFB) semiconductor lasers have the advantages of small size, low cost and mature manufacturing technology. However, their application scope is limited due to the MHz linewidth. The linewidth can be narrowed to the order of kHz by selfinjection locking with ring resonators, but there exists instability as the laser being locked. We selfinjection lock a DFB semiconductor laser to four different ring resonators and monitor the changes of optical power, polarization state and wavelength at multiple ports of the locking circuit. It is revealed that the factors affecting the locking stability of DFB semiconductor laser include resonant mode hopping, polarization state hopping, and phase change of the feedback locking loop caused by external temperature and vibration, and the dominant factors are different when different types of ring resonators are used. Control of these factors can improve the stability of the selfinjection locking of DFB semiconductor lasers, so that better application effect can be achieved for the selfinjection locked DFB semiconductor laser.

A kind of widebandwidth optical source applying amplified spontaneous emission of Er3+doped optical fiber is proposed, with bidirectional pumping and doublepass configuration. Experiments were performed to verify the proposed scheme, and then the output performance was optimized. The pump efficiency, spectrum flatness and stability were analyzed in detail. The experimental results show that the pump conversion efficiency is increased by 8.24%, the flatness of optical spectrum is improved by 1dB in 1525~1557nm without any filter，and the output linewidth @3dB is widened by 24.56nm. The stable output of optical power and spectrum within one hour is realized, which can provide light source for optical fiber sensing, spectral analysis, etc.

Aldoped ZnO (AZO) thin films were deposited on quartz glass by RF magnetron sputtering at room temperature with controlled working pressure, power and deposition time. The effects of three processing conditions on the microstructure and photoelectric properties of AZO thin films were investigated. After annealing at 500℃, all AZO films have hexagonal wurtzite structure and excellent transparency. The average transmittance of AZO films in visible light range is above 86%. At a pressure of 0.25Pa with the power of 200W, the resistivity of the thin film deposited for 10min is as low as 5.04×10-3Ω·cm, while the best performance index is 0.314×10-3Ω-1 for 15min. The results show that the crystal structure, square resistance and transmittance of AZO films prepared by magnetron sputtering are closely related to the working pressure, power and time during the preparation process, and the performance indexes can guide the optimization of AZO films preparation.

Polycrystalline MoO3 thin films were fabricated on silicon substrates at low temperature by plasmaenhanced atomic layer deposition (PEALD) using molybdenum hexacarbonyl and oxygen as precursors. Crystal structure, surface morphology, elemental composition of the deposited MoO3 films were characterized by XRD, SEM, AFM and XPS. Results show that the crystal structure and surface morphology of the fabricated MoO3 thin films are highly dependent on the substrate temperature and the pulse time of the oxygen plasma. When the substrate temperature is 170℃ and above, the asgrown film is αMoO3. Highly (0k0) preferorientated MoO3 thin films can be obtained at 170℃ by properly prolonging the pulse time of oxygen plasma to 60s. The films are followed by the island growth mode based on the AFM analysis.

Two kinds of micron diamond grain thin film were obtained by microwave plasma chemical vapor deposition method under different conditions. The composition of the two kinds of thin film were analyzed by Raman spectroscopy and Xray apparatus, and the surface morphology was analyzed by scanning electron microscope (SEM), and the field emission performance was studied by the field emission device with secondary structure. Finally, the characteristics of micron diamond films with excellent field emission properties were analyzed and discussed.

MoS2 is a kind of twodimensional semiconductor material with unique band structure. For fewlayer MoS2, the band gap decreases significantly with the number of layers. Accordingly, the magnetic tunnel junctions (MTJs) with MoS2 barrier will show abundant and various physical properties. In this paper, the temperaturebias phase diagrams are calculated, respectively, for MTJs with singlelayer MoS2, doublelayer MoS2, threelayer MoS2 and fivelayer MoS2 barrier under different half the exchange splitting of the ferromagnetic electrodes. The calculations show that, the MTJs with singlelayer and threelayer MoS2 barrier is suitable to be applied at low temperature. In particular, the MTJs with singlelayer MoS2 barrier possess excellent performance at high bias. The optimized region of MTJs with doublelayer MoS2 barrier is located at room temperature and low bias. Therefore, they are favorable for the application of information storage. Through regulating the parameter of the ferromagnetic electrodes, the MTJs with fivelayer MoS2 barrier can work throughout a wide power range. The above results lay a solid theoretical foundation for the application of MTJs with MoS2 barrier.

As a preprocessing step of target segmentation, superpixel can greatly reduce the amount of subsequent data processing, and plays a vital role in image segmentation. In most superpixel algorithms, seed points are sampled on a regular grid or initialized randomly, which easily leads to undersegmentation. In order to obtain a good distribution of seed point and avoid undersegmentation, an adaptively initializing superpixel seeds method based on Kmeans++ is proposed and used to improve the algorithms of SNIC. The experimental results show that the improved SNIC algorithm can get higher boundary recall rate and lower undersegmentation error rate than that of the traditional algorithm without a lot of computational cost.

An exposure control technique based on frame transfer CCD is proposed to greatly improve the dynamic range in hyperspectral image detection. It adopts a new working mode of integrating first and then reading out, combined with the fast charge dumping timing control method of chargecoupled devices (CCD), which can effectively remove the invalid charge in the idle period and realize fast switching between the ultrashort integration time and the long integration time exposure period. For the same detected target, the uninterruptable cycle exposure of multiple exposure cycles can be realized by fast switching between multiple integral cycles within a specified time range, so that the spectrum detection range index of this technique can be improved by more than 2 orders of magnitude compared with that of the traditional technology. At the same time, the dynamic setting mode of cyclic exposure file number and exposure time is designed. The timing simulation analysis and test verifies that the proposed design can effectively improves the adaptability of hyperspectral imaging technology in complex light environment.

Mobile edge computing (MEC) has emerged as a key technology to alleviate the computation workloads and decrease service latency for computationintensive applications by offloading the tasks to MEC servers. However, the existing computation offloading and resource allocation studies present some several problems: poor collaboration between edge servers; mismatch between the computational task arrival and the dynamic characteristics in the real environment; and the dynamic joint optimization problem of the collaborative task unload and resource allocation. To solve such issues, based on the collaborative MEC framework, a multiagent based deep deterministic policy gradient (MADDPG) is proposed for task unloading and resource allocation to minimize the overall longterm average cost. Simulation results reveal that the proposed scheme can reduce the delay and energy consumption.

Due to the restriction of aperture effect and the beam deviation, it is the common problem for phased array radar to get wide instantaneous bandwidth under wide scan scope. In this paper, a phased array beam forming system based on the microwave photonic technology was proposed, which can keep high consistency between the beampointing of receiving and transmitting modes and reduce the number of devices. The 16 channels TR community beam scanning system was built and tested. The experimental results show the system can realize beaming scanning under the wide scope of ±30° without beam deviation at Xband, and the beampointing of receiving and transmitting is highly consistent. Combined with the timesharing receiving and transmitting characteristic of the radar system, the scanning and detection capability of the phased array radar system can be effectively improved.

As a commonly used display device, digital micromirror device (DMD) uses the traditional pulse width modulation (PWM) method to display grayscale images, which can not meet the demand of high frame rate display due to the limitation of minimum pulse width. Thus we proposed a high frame rate display technology based on composite coding of illuminant and DMD in this paper. By adding the modulation of illuminant, the problem of exponential growth of bit plane display time with bit plane level caused by pulse width modulation is avoided. A display system consists of driver module, illuminant and DMD was built. In our test, by applying the illuminant modulation to lower 4bit and pulse width modulation to higher 4bit, the display system can achieve 2461Hz frame rate displaying 8bit grayscale image.

Aiming at the problem of increasing the number of optical elements and limiting the angle of view to balance the aberrations in the current optical design, which makes the optical system more complex, a design method of harmonic diffractive lenses based on the infrared waveband with a large field of view is proposed. The optical design software ZEMAX was used for optical design, a customizable surface profile was written using DLL, and this surface was used for partition optimization, and combined with scalar diffraction theory, the imaging effect was analyzed. The results show that the designed harmonic diffractive lens has a field of view of 21°, and the cutoff frequency (with 0.1 as the contrast limit) is 11.4lp/mm, and the feasibility of the lens with a large field of view single lens imaging is verified through experiments.