In掺杂CdMnTe晶体的Te气氛退火研究

Thermal annealing in Te vapor atmosphere was adopted to improve the properties of indium-doped Cd_1-xMn_xTe（x=0.2,CdMnTe） wafers grown by the vertical Bridgman method.The wafers before and after annealing were characterized by measuring the Te inclusions,etch pit density（EPD）,Mn composition,resistivity, and impurity.IR transmission microscopy and EPD measurements revealed that the densities of Te inclusions reduced from（5-9）×10⁴ cm^-3 to（2-4）×10⁴ cm^-3 and EPD from 10⁵ cm^-2 to 10⁴ cm^-2 after annealing. NIR transmission spectroscopy showed that the Mn composition increased by 0.002-0.005 mole fractions during the annealing.The resistivity of the wafers improved from（2.0-4.5）×10⁸Ω·cm to（1.7-3.8）×10⁹Ω·cm,which suggested that the deep-level donor of Te antisites was successfully introduced after annealing.Inductively coupled plasma-mass spectrometry（ICP-MS） revealed that the concentrations of impurities in the wafer decreased,which indicated the purifying effects of Te vapor annealing on the wafers.All the results demonstrate that the Te vapor annealing of the indium-doped CdMnTe crystal has positive effects on the crystallinity,resistivity and purity of CdMnTe wafers.     

应用于碲锌镉探测器逐次逼近模数转换器基准电压的研究

An on-chip reference voltage has been designed in capacitor-resister hybrid SAR ADC for CZT detector with the TSMC 0.35 μ m 2P4M CMOS process. The voltage reference has a dynamic load since using variable capacitors and resistances, which need a large driving ability to deal with the current related to the time and sampling rate. Most of the previous articles about the reference for ADC present only the bandgap part for a low temperature coefficient and high PSRR. However, it is not enough and overall, it needs to consider the output driving ability. The proposed voltage reference is realized by the band-gap reference, voltage generator and output buffer. Apart from a low temperature coefficient and high PSRR, it has the features of a large driving ability and low power consumption. What is more, for CZT detectors application in space, a radiation-hardened design has been considered. The measurement results show that the output reference voltage of the buffer is 4.096 V. When the temperature varied from 0 to 80℃, the temperature coefficient is 12.2 ppm/℃. The PSRR was-70 dB@100 kHz. The drive current of the reference can reach up to 10 mA. The area of the voltage reference in the SAR ADC chip is only 449×614 μm². The total power consumption is only 1.092 mW.     

一种应用于探测器上的抗激光致盲新方法

基于Ｆｒａｎｚ－Ｋｅｌｄｙｓｈ效应．提出了一种新型的提高（ＨｇＣｄ）Ｔｅ探测器抗激光致盲能力的新方法，同时给出了利用这种新方法实现自动保护功能的简单方案．并通过实验加以验证．证明这一方法能够大幅度提高（ＨｇＣｄ）Ｔｅ探测器的抗激光致盲能力。     

碲锌镉晶体中夹杂问题的实验研究

采用红外透射显微镜检测和研究了热解氮化硼(PBN)坩埚生长碲锌镉晶体(CdZnTe)中的缺陷—夹杂,并对夹杂的影响因素进行了分析。研究发现:不同原料的化学配比、自由空间体积、饱和蒸汽压、晶体生长温场对晶体中夹杂的种类、形状、密度和尺寸都存在着影响,通过一系列工艺的改进可以获得夹杂合格的碲锌镉晶体。     

自支撑GaN基核辐射探测器的Ⅰ-Ⅴ特性研究

使用自支撑GaN基材料制备了Schottky结构核辐射探测器,研究了探测器不同偏压扫描下的Ⅰ-Ⅴ特性.偏压从零偏向正偏扫描和从正偏向零偏扫描的Ⅰ-Ⅴ特性曲线并不重合;偏压从零偏向反偏扫描和从反偏向零偏扫描的曲线不重合性并没有正偏明显.测试并分析了PL谱图,得出Ⅰ-Ⅴ特性曲线不重合的原因是:从零偏到正偏的导电机制是热生载...     

应用于深紫外波段的AlGaN光电探测器研究

本文报道了肖特基二极管深紫外光电探测器的制备.此器件制作在GaN外延层上,其中外延层利用金属有机化学汽相沉积(MOCVD)的方法生长在4in的Si(111)片上.利用光谱响应度测量法确定GaN的截止波长在近紫外波段(200～400 nm);在紫外波段(5～20 nm),利用位于Berliner Elektronen speicherring-Gesellschaft ftir Synchrotronstrahlung (BESSY)的PhysikalischTechnische Bundesanstah(PTB)设备完成了绝对光谱响应度测量与同步加速器辐射.此工作是在欧洲空间局(ESA)支持的盲区太阳探测器项目框架下完成的.     

一维液晶缺陷光子晶体温度传感器的研究

将向列相液晶作为缺陷层引入一维光子晶体中,利用液晶折射率对温度变化敏感特性,设计了一维液晶缺陷光子晶体温度传感器。用传输矩阵法研究了传感器的温度特性,并用Matlab编程进行了模拟计算。结果表明,当温度升高时,液晶排列沿平行介质表面的传感器,缺陷峰波长向长波长方向漂移,缺陷模透射峰的宽度减小;而液晶排列沿介质表面法向的传感器,缺陷峰波长则向短波长方向漂移,缺陷模透射峰的宽度增大;传感器的温度灵敏度大于普通材料缺陷的光子晶体,与液晶材料和温度有关,温度接近液晶相变点而增大迅速;传感器缺陷峰波长的漂移与温度成非线性关系。设计了温度传感器探头结构和实验测量系统,测量结果与理论计算值符合。     

Nd:GGG激光晶体的缺陷研究

Nd:GGG晶体是热容固体激光器的一种重要的工作介质.采用提拉法沿〈111〉方向生长出直径为60 mm的Nd:GGG单晶,利用应力仪、偏光显微镜和环境扫描电子显微镜及化学腐蚀等仪器和手段,对晶体的宏观和微观缺陷进行了观察和分析,可为改善生长工艺、生长大尺寸优质Nd:GGG晶体提供指导.     

锑化铟晶体空位缺陷的正电子湮灭研究

锑化铟晶体材料的电学性能是影响最终制备的红外探测器件性能的关键因素。材料内部的杂质以及点缺陷特别是空位缺陷会极大的影响材料的电学性能,有时甚至会导致材料反型。本文利用正电子湮灭谱对锑化铟晶体材料的空位缺陷类型进行了研究,同时还对不同晶体生长拉速、导电类型晶体材料的正电子湮灭寿命进行分析。结果表明其内部主要为VIn型空位缺陷,且在一定拉速范围内,正电子湮灭寿命基本无变化,此外空位缺陷也不是导致N型锑化铟晶体材料导电类型反型的主要原因。     

基于CdZnTe晶体的2×2像素阵列探测器研究

根据CdZnTe(CZT)晶体的辐射探测理论,搭建了CZT像素阵列探测系统。采用241Am源研究了2×2像素阵列特性,得到了59.5keV能量γ射线能谱,最高能量分辨率为14.6%,并且各个像素性能差异明显,特别是边缘像素出现低能道区域计数增多,谱线向低能方向轻微漂移。为优化辐射成像,对实验数据作了进一步研究。结果表明,晶体内部不均匀的电场是造成各个像素性能偏差,和边缘像素谱漂移的主要原因。在成像过程中可以通过针对性的补偿加以修正,从而提高探测器有效成像面积,优化成像质量。     

Cooling process optimization to control Te inclusions for improving CdZnTe detector performance

Investigation of Te inclusion distribution in CdZnTe crystals treated by the cooling process at different rates indicated that cool slowly at 10–20 K/h caused the emergence of lower concentration but larger size Te inclusions, with a high level total volume fraction, decreasing the IR transmittance. When cooled fast, the dimension of Te inclusions reduced and the concentration increased, even the faster cooling rate, the higher the concentration; moreover the IR transmittance improved. The measurement of energy spectrum demonstrated that Te inclusions of large size or high concentration induced by slow or too fast cooling rate respectively degenerate spectroscopy performance. Cooling at 40–50 K/h presented an optimized process, which retained a certain amount but small size Te inclusions and kept a low total volume fraction, expressing better energy resolution.     

基于空间应用的红外探测器驱动电路设计

以空间应用为目的,提出基于国产1024×6长波红外探测器的驱动电路设计方案。该方案利用LDO和电压跟随器产生探测器需要的驱动电压。通过对该方案进行论证及在某型号空间相机中应用,证明该方案切实有效,能够较好的满足空间应用需求。     

Material properties of large-volume cadmium zinc telluride crystals and their relationship to nuclear detector performance

The material showing the greatest promise today for production of large-volume gamma-ray spectrometers operable at room temperature is cadmium zinc telluride (CZT). Unfortunately, because of deficiencies in the quality of the present material, high-resolution CZT spectrometers have thus far been limited to relatively small dimensions, which makes them inefficient at detecting high photon energies and ineffective for weak radiation signals except in near proximity. To exploit CZT fully, it will be necessary to make substantial improvements in the material quality. Improving the material involves advances in the crystallinity, purity, carrier lifetimes, and control of the electrical compensation mechanism. A more detailed understanding of the underlying material problems limiting the performance of CZT gamma-ray detectors is required; otherwise, problems with supply, delivery times, and unit cost of large-volume (>5 cm³ active volume) CZT spectrometers are expected to continue. A variety of analytical and numerical techniques have been employed to quantify crystallinity, strain, impurities, compositional and stoichiometric variations, bulk and surface defect states, carrier mobilities and lifetimes, electric field distributions, and surface passivation. Data from these measurements were correlated with spatial maps of the gamma-ray and alpha particle spectroscopic response, and feedback on the effectiveness of crystal growth and detector fabrication procedures has been generated. The results of several of these analytical techniques will be presented in this paper.     

Hydrogen transport vapor phase epitaxy of CdTe on hybrid substrates for x-ray detector applications

The growth of thick CdTe epitaxial layers by the hydrogen transport vapor phase epitaxy (H₂T-VPE) method is reported for the first time. The thermodynamics of the H₂ transport method of CdTe is analyzed to determine the equilibrium partial pressures of the molecular species in the vapor and its supersaturation as a function of growth conditions. (100)-oriented CdTe epilayers are successfully grown by H₂T-VPE on hybrid ZnTe/GaAs(100) substrates prepared by metalorganic vapor phase epitaxy. Growth rates up to 10 μm/h are obtained at temperatures ∼760°C and with the CdTe source temperature at 827°C. The achievement of even higher growth rates can be foreseen by using the present method under slightly different conditions; several hundreds micron thick CdTe layers can be thus grown by the H₂T-VPE. CdTe samples have mirror-like, nearly featureless surfaces. Also, CdTe epilayers have shown a medium-to-high resistivity at room temperature, possibly as a result of compensation by donor impurities diffusing from GaAs. Still the growth of highly resistive layers by in-situ chlorine doping during the H₂T-VPE growth is possible. In summary, H₂T-VPE is a potential alternative to traditional melt- and vapor-growth methods for the synthesis of detector-grade CdTe for application to the 1–100 keV x-ray energy range.     

Improvement of nonlinearity and extension of wavelength region using tandem (PV+PC) type HgCdTe detector (Dual-MCT) in FTIR spectrometer

A tandem (PV+PC) type HgCdTe detector (Dual-MCT) was fabricated to improve the nonlinear detector response and extend the wavelength region in Fourier transform infrared spectrometer. The backside-illuminated narrow band PV-MCT detector was arranged at the upper part of the hybrid device. A grid or a circular pattem electrode was formed on the active area to transmit the longer wavelength light than cutoff. The appropriate reverse bias was applied to the detector to obtain better linearity. The PC-MCT detector with a longer cutoff wavelength of middle band or wide band was arranged at the down part of the device to receive the transmitted light through the PV-MCT. The interferogram signals with better linearity from both detectors were combined after the phase matched preamplifier and Fourier transformed to a spectrum. The calibration curves evaluated with the absorption peaks at wavenumbers of 2025 and 972 cm⁻¹ of n-hexane showed that the Dual-MCT had excellent linearity and wider wavelength coverage.     

Optical-absorption model for molecular-beam epitaxy HgCdTe and application to infrared detector photoresponse

Accurate knowledge of the optical-absorption coefficient in HgCdTe is important for infrared (IR) detector design, production process (layer screening), and interpretation of detector performance. Measurements of the optical-absorption coefficient of HgCdTe layers with uniform composition are presented with the goal of developing a revised model in the interest of IR detector technology. Existing methods of determining HgCdTe alloy composition from IR transmission measurements are compared, where one self-consistent method is suggested and shown to agree with experimental detector data. An exponential Urbach and hyperbolic model are presented to represent band tail and above-bandgap absorption regions, respectively. Parameters associated with these models are extracted for Hg_1−xCd_xTe compositions of x=0.22–0.60 and temperatures of T=40–300 K using samples of varying thickness to obtain accurate data for varying spectral regions of the absorption coefficient. An initial analytical expression for the absorption coefficient is presented and compared to experimental detector-response data. Detector-response simulations indicate that accurate optical-absorption models are needed, where detector structures with thin layers and arbitrary composition profiles in current and future IR detectors will be the most demanding.     

空间光通信中应用于精密指向的面阵探测器的定位精度分析与验证

为了实现空间光通信中高精度的链路,本文重点研究了影响面阵探测器对于目标定位精度的关键因素。首先从机理上分析了质心算法的误差,并仿真验证了满足空间无损采样条件的必要性。我们定义了NU值并以此为指标来量化探测器的非均匀性,随着NU自0开始线性增长,质心的定位误差持续增长但是速度放缓。当NU值为0.005时,最大定位误差为0.043 像素。在目标入射到光学系统的光强不断改变的条件下,NU值越小,质心位置越接近光斑的真实位置。我们通过实验测试了某种典型的CMOS探测器在不同光照强度下的像元响应,建立了像元响应非均匀性的数理模型,计算出NU值于线性响应范围内在0.0045到0.0048范围内波动。光斑质心定位精度的实验结果表明,绝对定位误差小于0.05 像素,可以满足高精度链路的需求,验证了理论和仿真的有效性。     

Development of a 64 × 64 CdZnTe array and associated readout integrated circuit for use in nuclear medicine

Previous work has shown that hybrid semiconductor detector arrays similar to those used in infrared focal-plane arrays are very attractive for use in nuclear medicine and other gamma-ray imaging applications. In this paper, we describe the development of a 64 × 64 readout multiplexer specifically for use in gamma-ray imaging; we also describe the construction of 64 × 64 CdZnTe hybrid detector arrays using the new readout. The readout and detector array are both about one inch square (2.5 cm × 2.5 cm) and have 380 μm pixel pitch. Some initial assembly problems have been resolved by stabilizing the hybrids with epoxy. Preliminary testing results are presented that verify that the 64 × 64 CdZnTe arrays perform as excellent imaging spectrometers.