As the core component of the electron-bombarded active pixel sensor (EBAPS), the electron-sensitive CMOS (e-CMOS) can be prepared by thinning the surface layer of back-illuminated CMOS (BSI-CMOS), which was named electron sensitization. Due to the dramatic increase of dark current during the electron sensitization of BSI-CMOS, the signal-to-noise ratio and gain characteristics of the prepared EBAPS would be reduced. To solve this problem, this paper proposed a passivation strategy of SiO2 grown by plasma-enhanced chemical vapor deposition (PECVD) to inhibit surface defects, and the optimal SiO2 film thickness was explored through process optimization and electron bombardment system testing. As a result, the dark current was effectively suppressed (~50 e-1/s/pix), and a lower electron-sensitive threshold voltage of 550V was realized. Moreover, the defect states density of SiO2 deposited by PECVD was lower compared to Al2O3, which resulted from the more matched lattice coefficient of SiO2. Finally, EBAPS based on SiO2 passivated e-CMOS was realized, and high-quality imaging was successfully achieved at 1×10-4lx illumination. The above results showed that the SiO2 grown by PECVD can effectively suppress dark current at a thickness of ~5 nm, and reduce the electron-sensitive threshold voltage to 550 V, which provided technical support for the subsequent development of EBAPS devices with high gain and low noise.
Graphene is considered a suitable atomically thick layer on photocathodes, and the photoemission performance of the graphene-covered photocathodes can be enhanced through Cs/O activation. To investigate the effects of the substrate materials beneath the graphene layer on Cs/O deposition and photoemission performance. We compare the activation processes and photoemission performances of few-layer graphene supported by nickel and copper to investigate the effects of the substrate materials beneath the graphene layer on Cs/O deposition and photoemission performance. By Cs/O activation, the nickel-supported few-layer graphene can possess a higher response at 405 nm, while the copper-supported cathode can acquire a wider spectral response and better stability. After degradation, we discover that the samples supported by nickel and copper can act differently through the additional Cs/O deposition processes, while the surface barrier heights of both samples are further decreased.
For the current brightness gain and maximum output brightness adjustment method of image intensifier has low efficiency, time-consuming, low precision, and other problems, this paper firstly studies a communication protocol from the perspective of digital communication of auto-gating power supply microcontroller. By means of communication with the host computer, the corresponding parameters of the internal program of the auto-gating power supply microcontroller are adjusted. Secondly, the hardware interface of the whole tube communication of the image intensifier is designed. Finally, the calibrated experimental device is used to adjust the brightness gain and maximum brightness of the whole tube, and the automatic brightness control function of the adjusted whole tube is verified. The adjustment time is short, the adjustment precision is high, and the matching between the auto-gating power supply and the image tube can be better realized.
This paper proposed a "high-speed imaging + digital processing" evaluation method to solve the problem of scintillation noise of low light image intensifiers under low illumination, which fills the gap in the quantitative evaluation of scintillation noise characteristics under low illumination in China. It was found that the scintillation noise is mainly characterized by scintillations with a diameter over 50μm and a duration of sub-microsecond or less. The frequency and the brightness of the scintillations are used to quantitatively evaluate scintillation noise. The effects of the input illuminance and luminous gain on the scintillation noise of the domestic low light image intensifier were investigated by the proposed method. With the increase of input illuminance, the frequency of scintillation noise increases linearly, and the brightness does not change obviously. As the luminous gain of the image intensifier increases, the frequency of scintillation noise increases linearly, but the rate of increase in scintillation frequency is higher than that of luminous gain increase. Based on the characteristics of scintillation noise, such as size, duration, intensity, and the variation law with various conditions, the scintillation noise of the image intensifier can be further studied. The quantitative evaluation method of scintillation noise based on scintillation noise frequency and average equivalent input electron quantity proposed in this paper is of great significance to the breakthrough of scintillation noise and the improvement of the performance of image tubes under low illumination in the future.
Electron Bombardment Active Pixel Sensor (EBAPS) can work in photosensitive mode and electrical sensitive mode due to the special doping mode of CMOS. In both operating modes, after the target signal passes through the photoelectric conversion, gain and readout process of the EBAPS device, the readout signal needs to exceed the noise generated by the device to ensure the distinguishable output image. However, in the process of conversion and multiplication of the target signal, noise will inevitably be introduced. The noise will be amplified along with the signal, causing distortion or attenuation of the original signal, thus interfering with the quality of the output image and affecting human observation. Therefore, it is necessary to study the noise characteristics of EBAPS as a key factor affecting the imaging quality. For the development of high-performance EBAPS devices, this paper focuses on the noise characteristics of detection and imaging under different operating modes. By analyzing the working principle of EBAPS devices in different working modes, the noise sources that affect the imaging quality are obtained. In photosensitive mode, the noise of EBAPS is consistent with that of ordinary CMOS image sensor. These noises are mainly affected by CMOS process level, ambient temperature, working time and other factors, and can usually be removed by image processing algorithms. In the electric sensitive mode, the noise of EBAPS mainly comes from GaAs photocathode and the electron multiplication process of CMOS. These noises can be suppressed by reducing the working temperature, improving the surface defects and cleanliness during the chip preparation, and improving the doping process of the substrate. According to the noise generation mechanism, the noise suppression methods are proposed to obtain a high SNR digital output image. The above research provides some references for the following research on noise characteristics and noise reduction methods of digital low light level devices.
The underwater photoelectric detection equipment mainly uses 532 nm laser as the light source, and GaAlAs with Al component of 0.63 can obtain the cutoff wavelength near 532 nm, which is an excellent photocathode material to meet the requirement of narrow band spectral response of 532 nm laser. Furthermore, the light absorptance of the cathode can be improved effectively by the quadrangular prism or cylinder nanostructured arrays prepared on the reflection-mode Ga0.37Al0.63As cathode surface, and the maximum light absorptance can reach 96.2% at 532 nm, when the cylinder nanostructured array with a height of 900 nm and a base width of 100 nm. Nevertheless, the Ga0.37Al0.63As cathode with the quadrangular prism nanostructured array is less influenced by the incident angle of light.
Low-light-level night vision technology, as the sign of the development of national military science and technology, has received extensive attention in recent years. However, the gray-scale level images provided by traditional low-lightlevel night vision devices are unable to meet the requirements of modern war, color night vision technology developed accordingly. This article mainly discusses the development of night vision technology and several technical methods for obtaining color night vision images, including indirect methods based on color conversion or fusion, and direct methods based on hardware, which provides reference for researchers to understand the color night vision technology.
KEYWORDS: Image processing, Image enhancement, Image information entropy, Night vision, Digital image processing, Digital Light Processing, Detection and tracking algorithms, Visualization, Optoelectronics, Infrared technology
When the classical gray stretching algorithm is applied in digital low light level devices, it cannot meet the requirements of illumination environment change in large dynamic range, and the image processed under very low illumination or very high illumination is prone to the loss of target details, an adaptive gray stretching algorithm suitable for digital low light level devices is designed. The algorithm adds the variable of the brightness value of the original image information collected by the digital low light level device to the gray stretching transformation matrix, deduces the current environmental illuminance value according to the transformation of the brightness value, timely adjusts the relevant parameters in the gray stretching calculation matrix according to the environmental illuminance value, and obtains the gray stretching transformation matrix suitable for different image features under different illuminance environments, In order to meet the requirement that digital low light level devices should be suitable for the change of illumination environment in a large dynamic range. This paper also compares the adaptive algorithm with the classical algorithm, and gives the test results. At the end of the paper, the operation efficiency of the algorithm is tested to verify that the algorithm can meet the requirements of real-time image processing speed of digital low light level devices.
Aiming at the problem of the lack of comprehensive and objective evaluation methods for near-infrared and low-light-level multi-band fusion images, this paper proposes a multi-dimensional fusion image quality evaluation model that conforms to the interpretation habits of the human visual system. Firstly, the multi-source fusion image quality of low illumination CMOS, ICCD, EBAPS devices and near-infrared InGaAs detector is subjectively evaluated. Secondly, 14 classical evaluation indexes such as information entropy, mean gradient, mutual information and structure similarity are combined. The parameters of each index are dynamically adjusted, and finally an objective evaluation model is established based on the linear regression model. The SROCC, KROCC, PLCC and RMSE values of the optimized objective evaluation model and subjective evaluation score are 0.88, 0.72, 0.89 and 0.38, respectively, indicating that the accuracy and stability evaluation effect of the objective model is better. It solves the limitation of single factor evaluation index and realizes the comprehensive and objective quality evaluation of multi-source detector fusion image, which provides theoretical support and decision basis for the selection of night vision camera in complex illumination environment and the data fusion of multi-detector in low illumination condition. < <
Underwater photoelectric detection equipment with 532 nm laser as light source needs to match specific photocathodes to achieve the purpose of high quantum efficiency and narrow-band response. NEA GaAlAs photocathodes have a series of advantages, such as high quantum efficiency, adjustable spectral response cutoff threshold and long lifetime to serve as the devices for underwater detection. However, the quantum efficiency of GaAlAs photocathodes is not high enough to meet the actual detection requirements. In addition, micro-nano structures on the surface of materials have been proved to be an effective method to improve optical absorption. In this paper, four kinds of nanostructures including square column, cylinder, square cone and cone are designed. By the finite difference time domain method, results show that the optical absorptivity of reflection-mode GaAlAs photocathodes can be effectively improved. The optical absorptivity of square cone nanostructures increases and tends to be stable with the increase of filling factor. The optical absorptivity is approximately 100% at blue-green light region including 532 nm, and has an abrupt cutoff feature. Otherwise, when the absorptivity of square cone nanostructures is high and stable, the most intense light absorption part will move to the top of nanostructures with the increase of filling factor, thus effectively shortening the electron transport distance and improving the photoemission capability.
In order to research H+ beam radiation on photoelectric performance of GaAs photocathodes used in low-light-level optoelectronic devices, based on Monte-Carlo method, quick calculation of damage, along with effects of Cs and Cs-O activation layer on ion trajectory, performance, ionization of ions and recoils are discussed. From the simulation results, the average stopping range increases with the increase of incident energy, and the dispersion varies with the incident angle, the minimum dispersion at 1 keV is obtained at 60° when Cs-O ratio is 2:1, and the minimum dispersion at 2 keV is obtained at 60° when Cs-O ratio is also 2:1. In addition, the produced vacancies increase with the incident energy while the value is almost not influenced by the incident angle, and the backscattered ions increase as the incident angle increase both in 1 keV and 2 keV cases, and decrease with the incident energy. Also, ionization dominate the H+ ion bombarding process instead of producing vacancies and phonons. With the increase of incident energy, the percentage of ionization of ions increases, while those of phonons of ions and ionization of recoils decrease. However, the corresponding percentages of ions and recoils remain nearly unchanged with the increase of incident angle and the variation of composition of Cs or Cs-O activation layer.
The color information in the true color low light level night vision image is the true restoration of the visible light color information reflected by the scene itself. Compared with the gray-scale level image and the false color image, it can obtain more abundant image information, which is more in line with the observation habit of the human eye and reduce the fatigue of the human eye. Under the background of information war, aiming at the multi-functional, all-weather, information sharing and transmission characteristics of new type of low light level equipment for single soldier, the requirements of digitalization, high integration and low power consumption are put forward for the true color low light level night vision technology. In this paper, the research progress of real color digital night vision technology is reviewed: firstly, the classification of color night vision technology is introduced; then, the foreign true color digital night vision products represented by French photonis company, Japanese komamura company and American SPI Infrared company are summarized, included the technology route and development level of the true color digital night vision technology; finally, three issues that need to be considered in the realization of low light level night vision true color technology are proposed.
In view of the attenuation of performance index of self-developed EBAPS detector principle sample with the increase of working time and working temperature, a test method is designed from the angle of dark current noise and working temperature change, and the corresponding relationship between dark current and working temperature of EBAPS device is tested. Because EBAPS detector combines the characteristics of solid-state and vacuum micro-optical devices, it inherits the characteristics of dark current of CMOS chip changing with temperature. With the increase of temperature, dark current of CMOS chip increases rapidly. The rise of dark current will directly affect the equivalent background illumination of EBAPS detector. If the effective signal received by the detector is lower than the dark current noise signal at low illumination, that is, the effective signal is lower than the equivalent background illumination; the effective signal will be obscured in the noise signal, leading to the detector not working properly. In view of the characteristics of EBAPS detector, the test and calculation are also carried out. The data relations and change curves between the operating temperature, dark current and equivalent background illumination of EBAPS device are given. At the end of the paper, methods and ways to optimize the imaging performance of EBAPS detectors are presented, such as image processing algorithm, reducing the power consumption of readout circuit, and optimizing the dark current suppression process of EBAPS devices.
Low-light-level (LLL) images, which are captured in the extreme environment without enough light for human eyes. LLL images quality degenerates badly with light decrease. The heavy noises and low contrast of the LLL images impede the access to the targets information. In order to enhance LLL images, we propose a two-step method to remove the complex noises. First, median filtering is adopted to remove the salt and pepper noises which are often introduced from the bad pixels. Second, the four-direction nonlocal means algorithm is adopted. The experimental results show that the proposed method can remove the noises and keep the details of the low illumination level scene effectively.
KEYWORDS: Signal to noise ratio, Ultraviolet radiation, Field programmable gate arrays, Microchannel plates, Night vision, Gold, Semiconductors, Light, Power supplies, Lamps
In the field of low-light night vision, EBCMOS (Electron Bombarded Complementary Metal Oxide Semiconductor) has received much attention due to its high-gain, high-resolution, low-noise, etc. The techniques used to test EBCMOS performance are also in urgent need of development. According to the composition of EBCMOS detectors, based on the existing vacuum device and semiconductor device test methods, the SNR testing method of EBCMOS is proposed and the testing system is designed. The Field Programmable Gate Array(FPGA)-based hardware platform is built in the vacuum environment. The CMOS data is read out by programmable logic design. Finally, the SNR is obtained by the MFC host computer. Experiments show that the system can measure accurate SNR parameters.
KEYWORDS: Night vision, Image segmentation, Image processing, Image enhancement, Detection and tracking algorithms, Human vision and color perception, Visualization, Optical engineering
Since low-light-level images are generally grayscale images that lack color information, it is necessary to colorize these images to enhance human vision for night vision scene. In this paper, a low-light-level image colorization method is proposed based on Laws’ texture feature descriptor. Laws’ filter can analyze the texture features of the image, which are the pointers we used to find the corresponding color information for low-light-level gray images from the reference color image. The experimental results demonstrate that our colorization method can make night vision images have colors closer to natural perception and help observers better understand night vision scenes.
Negative-electron-affinity GaAs-based photocathodes have already found widespread application in modern night vision detectors and vacuum electron sources. Considering the importance of surface micro-area analysis for cathode preparation, a new ultrahigh vacuum interconnection system for photocathode preparation and characterization was developed, wherein the scanning focused X-ray imaging positioning technique combined with the X-ray induced secondary electron image was applied to characterize the surface components in the specified micro region of semiconductor photocathodes. With the aid of the advanced characterization technique, the surface components of micro regions of interest for GaAs cathode samples after cleaning and Cs-O activation were analyzed. The experimental results show that the GaAs cathode samples would be subjected to secondary contamination from the metal sheet of sample holder, accompanied by a small amount of sodium and cesium. The subsequent heat treatment and Cs-O activation can hardly remove the sodium contamination, which can affect the arsenic desorption during heat treatment, hinder the Cs-O adsorption in the activation process, and finally reduce the photoemission performance of the activated cathode. Through the application of the X-ray induced secondary electron image, the optimal cleaning method for GaAs cathode was investigated. This surface characterization technique is of practical value to improving analysis accuracy and optimizing the cathode preparation process.
With the development of the state grid, there is a great demand for equipments to detect the corona discharge on high-voltage transmission lines. The uncooled infrared image and solar-blind UV image fusion camera is supposed to achieve the purpose. Image fusion is an important method to integrate the features from images of different band spectrum into a single frame for enhanced visual perception. The image fusion camera consists of infrared channel, solar-blind UV channel, imaging processing module and display module. An image fusion rule based on the Laplacian pyramid decomposition is proposed. The fusion methodology is divided into several steps: image preprocessing, Gaussian pyramid decomposition, Laplacian pyramid decomposition, image fusion and reconstruction. The algorithm is implemented on the image fusion camera. The camera is verified to detect the corona discharge for fault diagnosis of high-voltage power system. Keywords: uncooled infrared FPA, image fusion, solar-blind UV, corona discharge
As the rapid development of back-illuminated CMOS (BI-CMOS) image sensor technology in recent years, its application prospect in the field of Low-Light-Level (LLL) night vision has been widely concerned. Therefore, LLL imaging module was developed based on BICMOS, whose 3-D noise data was obtained under different illumination conditions. The test results show that, the signal-to-noise ratio (SNR) of imaging module becomes worse with the decreasing of illumination. According to the judgement of noise, the noise power of the image in low illumination is mainly Gaussian distribution. And the image processed by spatial filtering, which efficiently reducing the imaging noise and improving the imaging quality.
Based on the study of working principle and making process of 4-transistor Backside-illuminated CMOS (4T BSI-CMOS), Signal-to-noise ratio (SNR) model are established and quantitative calculating formula is derived. In addition, factors of influencing SNR are analyzed. Two methods are presented to enhance the SNR, the one is optimizing structure of 4T BSI-CMOS image sensor to strengthen the signal and the other one is correlated double sampling to decrease fixed pattern noise (FPN). These results serve as useful guidelines to enhance the SNR of 4T BSI-CMOS and improve the image quality.
Night vision technologies have been used in military and civilian monitor wildly. In this paper, an image fusion camera based on Infrared FPA, ICMOS and FPGA is designed. First, image acquisition module consist of bias voltage, AD circuits and optical system is built. The MCP in front of the CMOS ensures the gain up to 104. Then, Verilog is written to drive these two sensors, pre-proceed the images data and push them into LPDDR. Moreover, we propose a fully parallel algorithm to fuse the images in real time using gradient. This algorithm neither needs iteration nor morphology, so it dose not consume the band width of LPDDR. Finally, video is output in PAL format.
Low Level Light (LLL) night vision technology is extensively applied in national defense and civil application fields. The digitization of LLL imaging is trend of light detection technology in the future. The corresponding modulation transfer function (MTF) and total system MTF model were established, base on the structure composition and operation principle. Simulation was carried out to analyze the performance of the MTF modern. Results indicate that the MCPCMOS better contrast of object. When the spatial frequency increasing, the MTF of MCP-CMOS downing faster than that of GaAs LLL image intensifier. The GaAs image intensifier shows an better image restoration capability and higher limiting resolution. The model and simulation results can provide a theoretical guidance for the fabrication and application of high imaging quality MCP-CMOS.
KEYWORDS: Adsorption, Chemical species, Chemical elements, Gallium arsenide, Gallium, Chemisorption, Night vision, Visual process modeling, Optoelectronics, Oxidation
Using the projected augmented wave potential by the density functional theory based upon gradual gradient approach method and the slab model, from the calculated surface, we identify the relaxed atoms sites of GaAs(110) surface, the electronic structure of elements K and O adsorpted on binding sites of ideal GaAs(110) surface have also been calculated, especially the total energy of the adsorption system. The comparison results of calculated total energy showed: for K and O elements at highest coverage of Θ=1ML on GaAs(110) surface, they were not formed to local domain of competitive chemical adsorption, while they were formed to a compound uniformity phase of cooperative chemical adsorption. Our calculated results providing theoretical basis and reference for the application of alkali oxidation adsorpted on GaAs surface to form a negative electron affinity photocathode.
As an III-V semiconductor material, InxGa1-xAs can response from 0.87μm (GaAs) to 3.5μm (InAs) by tuning the relative amount of Gallium in the alloy. In order to get better the response of the photocathode in near infrared
radiation region (1~1.7μm), InGaAs/InP heterostructure is widely used for photocathode material. The only
composition of In0.53Ga0.47As is lattice matched to the InP substrate and their spectral response is from 0.9μm to 1.6μm. thus In0.53Ga0.47As/InP heterostructure is selected for near infrared response photocathode. The In0.53Ga0.47As layer has been grown on InP substrate used for photocathode by solid source molecular beam epitaxiy (SS-MBE). The photocathode samples were grown to optimize the growth temperature, III/V ratio and growth rate. The In0.53Ga0.47As layer crystalline quality and component were performed by applying high resolution X-ray diffractometer, surface roughness investigations were performed by applying atomic force microscopy. The
Be doping characteristic was checked by the electrochemical capacitance-voltage(ECV). The optical performance of the photocathode is measured by the spectral meter. The collected information is being used to correct and enhance growth characteristics and optimize InGaAs/InP photocathode structure to increase spectral response and quantum efficiency.
The ideal status of the GaAs photocathode bonding assembly is as fellows: the GaAs photocathode should
not have additional stress; the crystal lattice should keep integrity after deposited Si3N4 reflection reducing
coating and bonging process that GaAs epitaxial material on a glass window. In order to estimating the
bonding quality of the GaAs photocathode bonding assembly, integral photoluminescence intensity was
calculated on the ideal bonding condition. Assuming the energy of incident light was absorbed by GaAs
active layer except reflection, according to the optical character of the GaAs photocathode bonding
assembly, the value was calculated. This value could be the standard to assess the quality of the GaAs
photocathode bonding assembly and improve the bonding technology that the GaAs epitaxial material is
bonded to a glass window.
KEYWORDS: Ions, Ion beam finishing, Monte Carlo methods, Transmittance, Microchannel plates, Scattering, Particles, Chemical species, Solids, Molecules
The simulation calculation and analysis on the electron transmittance and ion stopping power for ion barrier films (IBFs)
of BN were performed by Monte Carlo methods. The interaction model between particles and solids were described. We
find the Dead Voltage of BN IBFs is 220V. When the energy of the incident ions is 0.2~0.3KeV, 91%—99% of C+, N+ and O+ are stopped by BN IBFs; while 12%—19% of H+ for BN IBF. The results indicate that BN is an idea candidate for ion barrier films. This work provided a theory support for fabricating high performance low-level-light device.
The simulation calculation and analysis of electron back-scattering characteristics for ion barrier films (IBFs) of Al2O3
was performed by Monte Carlo methods. A physical model for the interaction of low-energy electrons with solid was
described. Trajectory and spatial distribution of the electrons were simulated with MATLAB software.The maximum
ratio of the back-scattered electrons was 19% at the incident energy of 0.24 keV. Beyond this value, the number of backscattered
electron decreased slowly with the increase of the incident energy. The back-scattering ratio increased almost
linearly with the increase of IBF density. When the incident energy was 0.7 keV and the film thickness is higher than 7
nm, the electron back-scattering ratio was always ~17% for the Al2O3 IBF. This work provided a theory support for
fabricating high performance low-level-light device.
The GaAs photocathode has been widely used in optoelectronic devices such as image intensifiers and
photomultiplier tubes, but it is inevitable for these devices to withstand a variety of mechanical shock. In order to study
the impact on the GaAs photocathode’s photoemission performance caused by mechanical shock, GaAs photocathode
image intensifier is researched in this paper . The spectral response of the GaAs photocathode was tested respectively
before and after several value of mechanical shock(the value of mechanical shock:55g,65g,75g,85g and 95g).The
parameter of the GaAs photocathode can be calculated and the quantum efficiency curve can be fitted as well using the
MATLAB software. The results show that surface escape probability is increased after photocathode is subjected to
mechanical shock, so that its photoemission performance will be improved. We think this phenomenon is due to the
GaAs photocathode surface Cs-O reconstruction. This finding provided a new method to enhance the photoemission
performance of photocathode.
KEYWORDS: Oxides, Data storage, Chemical reactions, Failure analysis, Analytical research, Capacitance, Reliability, Chemical analysis, Accelerated life testing, Process control
This paper investigates date retention ability of EEPROM cells for a given voltage or temperature by theory and
experiment. The expression of EEPROM date retention is derived. In the temperature acceleration experiment, the
logarithm of device inactivation time have linear ratio with temperature according to Arrhenius formula and the device
life retention was acquired in the various temperature. According to Arrhenius equation, lifetime curve is deduced. In the
electric acceleration experiment, because of the charge leaking on the floating-gate, the threshold voltage would decrease
gradually. In the log-log plot, the decrease efficiency of threshold voltage have linear ratio with time. Under the
assumption that the charge loss mechanism is Fowler-Nordheim tunneling through the thin oxide, date retention time of
EEPROM cells is derived and the experience formula is derived by experiment.
A comparative study of semi-insulating GaAs substrate, p-AlxGa1-x As/ semi-insulating GaAs and p-GaAs/p-AlxGa1-xAs/ semi-insulating GaAs structure has been done using the surface photovoltage (SPV) spectroscopy in metal–insulator–semiconductor (MIS) configuration. Which space charge region (SCR) dominated contribution to SPV in a certain wavelength range was determined. The SPV signals were calculated in a similar way as the open circuit voltage of an illuminated photodiode. One-dimensional continuity equations was adopted for determine the distribution of excess
minority carrier. The ideality factor of MIS configuration was investigated in air ambient. The contributions for SPV
signal of different layers were discussed in detail. At last the minority carrier diffusion length of different layers and
surface or interface recombination velocity were simulated.
There has been extensive applcations in the area of photoelectronic device because InGaAs grown on the GaAs substrate have advantageous photoelectronic performance and adjustable band gap. The main obstacle to acquiring high crystalline quality of InGaAs grown on GaAs substrate comes from the large lattice mismatch between InGaAs overlayer and GaAs substrate. It is particularly detrimental to the structure and photoelectronic property of InGaAs thin films that lager roughness of surface and high misfit dislocation density is introduced because of the defect onset during the growth. The In0.1Ga0.9As layers with and without linearly graded buffer layers grown on GaAs substrate had been studied. The investigations were performed by applying atomic force microscopy (AFM), high resolution X-ray diffractometry (HR
XRD). A linearly graded buffer layer is effective for lowering the misfit dislocation density in In0.1Ga0.9As layers on a GaAs substrate, but it can not end the dislocation in buffer layer completely. All above-mentioned is also confirmed in HRXRD results.
We report growth of high Aluminum content and heavy P type doping AlGaAs by molecular beam epitaxy (MBE) for
extended blue photocathode window layer. The key factors which affect of extended blue photocathode window AlGaAs
layer during epitaxy growth were analyzed and show that growth conditions such as V/III flux ratio, substrate
temperature and growth rate have dramatically effected on the AlGaAs layer crystalline quality and morphology. On the
basis of the optimized V/III flux ratio and appropriate growth rate, the substrate temperature for sample growth was
adjusted, the P type heavy doping(≥5×1018cm-3) and large area AlGaAs single crystal material with excellent crystalline
quality and good luminescence properties was fabricated on GaAs (100) substrate. The morphology of the samples was
checked by high resolution optical microscopy. The crystalline quality of samples was measured by X-ray diffraction and
luminescence property was measured by integral luminescence system. The relationship of the crystalline quality and
substrate temperature was got. The excellent crystalline quality AlGaAs layer obtained have been applied to GENIII
photocathode windows layer and spectral response range of photocathode extended to blue-green light in short wave.
The Quantum efficiency in the blue-green wave range of GENIII photocathode is enhanced.
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