Ga1-xAlxAs/GaAs光阴极光谱响应向短波延伸的机理分析和实验研究

为了实现光阴极光谱响应向短波延伸，分析了Ga1-xAlxAs/GaAs三代微光光阴极光谱响应向短波延伸的机理，提出了准禁带宽度的概念，讨论了Ga1-xAlxAs的禁带宽度随铝组份x值的增加而逐渐变宽的变化规律，计算了不同铝组份下光阴极光谱响应的短波限。通过提高光阴极材料的铝组份，做出了宽光谱响应像管，并给出了相应的光谱响应曲线。通过与标准三代微光像管光谱响应对比，发现：所得光谱响应曲线不仅向短波方向得以延伸，而且理论设计与实验结果吻合很好。     

透射式GaAs光阴极的静电键合粘结

提出了用于GaAs光阴极粘结的静电键合方法.相比于传统的热粘结方法,该方法温度低（350℃）,时间短（5 min）,在空气中进行.所制得的GaAs光阴极在激活台内的峰值灵敏度为68.8 mA/W（峰值波长为830 nm）.以此制作的三代微光管的积分灵敏度为1 311 μA/lm,优于传统的热粘结工艺制作的微光管的灵敏度(～1 200 μA/lm).     

积分光荧光测试在三代微光像增强器光阴极制作中的应用

本文基于半导体材料积分光荧光测试的原理,叙述在三代微光像增强器光阴极组件制作工艺过程中光荧光强度的变化规律及其测试结果,对其作出理论解释,并且说明如何依此规律对工艺过程进行监控。     

The optimal thickness of a transmission-mode GaN photocathode

A 150-nm-thick GaN photocathode with a Mg doping concentration of 1.6×1017cm-3 is activated by Cs/O in an ultrahigh vacuum chamber,and a quantum efficiency(QE) curve of the negative electron affinity transmission-mode(t-mode) of the GaN photocathode is obtained.The maximum QE reaches 13.0% at 290 nm.According to the t-mode QE equation solved from the diffusion equation,the QE curve is fitted.From the fitting results,the electron escape probability is 0.32,the back-interface recombination velocity is 5×104 cm·s-1,and the electron diffusion length is 116 nm.Based on these parameters,the influence of GaN thickness on t-mode QE is simulated.The simulation shows that the optimal thickness of GaN is 90 nm,which is better than the 150-nm GaN.     

MCP参数对微光像增强器分辨力影响研究

为了全面分析微通道板(MCP)参数对微光像增强器分辨力的影响,利用电子散射理论分析了MCP输出电子横向散射和MCP非开口面的电子散射情况,得到了MCP通道间距、输出电极结构和开口面积比等参数对微光像增强器分辨力的影响.分析结果指出:通过减小通道间距、采用MCP输出面镀多层电极或增加MCP输出端电极深度实现减小MCP输出电子横向扩散、增加开口面积比等,提高整个微光像增强器的分辨力.试验证明该方法有助于提高微光像增强器分辨力.     

Comparison of blue–green response between transmission-mode GaAsP-and GaAs-based photocathodes grown by molecular beam epitaxy

In order to develop the photodetector for effective blue–green response, the 18-mm-diameter vacuum image tube combined with the transmission-mode Al_(0.7)Ga_(0.3)As_(0.9)P_(0.1)/GaAs_(0.9)P_(0.1) photocathode grown by molecular beam epitaxy is tentatively fabricated. A comparison of photoelectric property, spectral characteristic and performance parameter between the transmission-mode GaAsP-based and blue-extended GaAs-based photocathodes shows that the GaAsP-based photocathode possesses better absorption and higher quantum efficiency in the blue–green waveband, combined with a larger surface electron escape probability. Especially, the quantum efficiency at 532 nm for the GaAsP-based photocathode achieves as high as 59%, nearly twice that for the blue-extended GaAs-based one, which would be more conducive to the underwater range-gated imaging based on laser illumination. Moreover, the simulation results show that the favorable blue–green response can be achieved by optimizing the emission-layer thickness in a range of 0.4 μm–0.6 μm.     

A theoretical and experimental evaluation of III-nitride solar-blind UV photocathode

We have developed a superior solar-blind ultraviolet (UV) photocathode with an Al_xGa_1-xN photocathode (x ～ 0.45) in semi-transparent mode, and assessed spectra radiant sensitivity related to practical use. Before being grown over a basal plane sapphire substrate by low-pressure metal organic chemical vapor deposition (MOCVD), a reasonable design was made to the photocathode epitaxy structure, focusing on the Al_xGa_1-xN: Mg active layer, then followed by a comprehensive analysis of the structural and optical characterization. The spectra radiant sensitivity is peaked of 41.395 mA/W at wavelength 257 nm and then decreases by about 3 to 4 decades at 400 nm demonstrating the ability of this photocathode for solar-blind application prospects.     

向短波红外延伸的微光夜视技术及其应用

对传统的微光像增强器与向短波红外延伸的InGaAs光阴极像增强器进行了比较,分析了通过调节组分而使响应波段覆盖夜天光辐射主要波段的InGaAs材料特性,揭示了以InGaAs半导体材料为光阴极的像增强器将在夜间具有更高的量子效率和响应度。介绍了InGaAs器件技术的国内外研究现状,InGaAs光阴极微光器件在短波红外波段的辐射响应是传统像增强器的100~1 000倍,InGaAs全固态探测器可在0.4 m~1.7 m宽光谱成像,在0.9 m~1.7 m范围的量子效率大于80%,表明该器件在激光探测、远距离定位与跟踪、情报侦察、夜间辅助驾驶等方面可以获得广泛应用。     

前近贴脉冲电压对三代微光像增强器halo效应的影响

为了探讨三代微光像增强器的合适工作电压,研究了前近贴脉冲电压对微光像增强器halo效应的影响.将脉冲电压信号加在光电阴极上,分别改变脉冲信号的高低电平电压幅值和占空比,利用高分辨率CCD采集了微光像增强器的halo图像,对比分析了halo图像中心线上各像素点对应的灰度值分布和光子计数.研究结果表明,随着高电平电压幅值和占空比的提高,灰度值为255的像素点数目变多,halo图像中背景和信号的边界越来越清晰.当前近贴电压增加到200 V以上和占空比大于60％左右时,其对三代微光像增强器halo图像中心线上各像素点的灰度值分布影响不大.当低电平电压增加到2V以上时,光电子在低电平阶段无法克服阻滞场到达微通道板.此研究有利于探讨微光像增强器的最佳工作电压和光电子从阴极面出射时的能量分布,为提高三代微光像增强器的性能提供了实验支撑.     

微光像增强器近贴距离在线测试方法研究

鉴于近贴距离尤其第一近贴距离是影响分辨力最重要的因素,提出一种新的微光像增强器近贴距离在线测试方法。应用平行平板电容器原理,通过测量阴极面和微通道板输入面之间的电容值来测量第一近贴距离。利用多组电容值和第一近贴距拟合出二者的函数关系式,通过精度分析,对函数关系式进行了修订及验证,测量最大偏差11.9%,满足精度要求。借助在线监控测试第一近贴距离,使压封过程处于受控状态,以便实现近贴距离的精密调控,达到提高微光像增强器分辨力的目的。该方法可推广到其他小间距的在线监控测试。