光伏型碲镉汞探测器在波段内连续激光辐照下的两种不同过饱和现象的产生机理

利用连续波段内激光对两批光伏型碲镉汞探测器进行了激光辐照实验, 发现了两种不同的过饱和现象. 实验表明, 光伏型碲镉汞探测器在强光辐照下都会出现开路电压随光强增强而减小的过饱和现象, 明晰了PV型探测器在强光辐照下的一般规律性现象和由探测器个体差异导致的特殊现象. 从等效电路模型出发, 剖析了两种过饱和现象的发生条件, 建立了数值计算的理论模型, 对两种过饱和现象进行了数值模拟, 计算结果与实验结果符合得较好. 研究表明, 光伏型碲镉汞探测器在波段内强光辐照下引起的过饱和现象有两种产生机理, 一种是热效应引起的暗电流增大机理; 另一种是探测器材料中缺陷引起的漏电流增大机理. 关键词： 波段内连续激光 光伏型碲镉汞探测器 过饱和现象     

光伏型光电探测器的激光软损伤机制

 对激光辐照功率密度高于探测器饱和阈值而低于其破坏阈值（中等功率的激光）时光伏型光电探测器的软损伤进行了理论研究,提出了一种新机制。当激光辐照功率密度超过探测器的饱和阈值以后,载流子的带间跃迁达到深度饱和,在半导体内产生热载流子且热载流子的温度高于晶格的温度,从而导致了光伏型光电探测器的电压输出信号随着辐照光功率密度的增加而下降直到零压输出的现象。对激光辐照下光伏型HgCdTe探测器的输出信号进行了模拟计算,结果表明,辐照光功率密度处于一定范围内探测器的输出信号随着辐照光功率密度的增加而逐步下降,甚至接近于零,与实验结果相符合。     

光伏型光电探测器的激光软损伤机制

对激光辐照功率密度高于探测器饱和阈值而低于其破坏阈值（中等功率的激光）时光伏型光电探测器的软损伤进行了理论研究,提出了一种新机制。当激光辐照功率密度超过探测器的饱和阈值以后,载流子的带间跃迁达到深度饱和,在半导体内产生热载流子且热载流子的温度高于晶格的温度,从而导致了光伏型光电探测器的电压输出信号随着辐照光功率密度的增加而下降直到零压输出的现象。对激光辐照下光伏型HgCdTe探测器的输出信号进行了模拟计算,结果表明,辐照光功率密度处于一定范围内探测器的输出信号随着辐照光功率密度的增加而逐步下降,甚至接近于零,与实验结果相符合。     

光伏半导体器件对能量小于禁带宽度光子的响应机理研究

利用光子能量为0.12 eV的10.6 μm连续激光分别辐照了禁带宽度为0.91和0.33 eV的光伏碲镉汞探测器. 实验表明,激光辐照下禁带宽度为0.91 eV的探测器输出正电压,而禁带宽度为0.33 eV的探测器对激光的响应方向却与之相反. 为了研究此现象,利用功率密度一定的10.6 μm激光辐照不同开路电压状态下禁带宽度为0.91 eV的探测器,实验结果证实初始开路电压是产生输出电压反向现象的原因. 对这一机理进一步分析发现,光伏探测器在光子能量小于禁带宽度的激光辐照下,其开路电压是热激发载流子导致的热生电动势和自由载流子吸收导致的晶格热效应共同决定的. 关键词： 能量小于禁带宽度的光子 光伏碲镉汞探测器 热生电动势 晶格热效应     

光伏碲镉汞探测器在波段内连续激光辐照下的非线性响应机理研究

利用波段内连续激光, 辐照禁带宽度为0.33 eV的中波光伏碲镉汞探测器. 实验结果表明, 随着辐照激光光强的逐渐增大, 探测器从线性响应过渡为非线性响应. 当探测器进入非线性状态, 探测器的开路电压随激光光强的增大而减小, 且在激光开启辐照时开路电压信号迅速下跳, 在激光停止辐照时开路电压信号迅速上跳. 通过考虑激光辐照下探测器的温度场分布以及温度对p-n结内建电场的影响, 结合考虑机械快门在开启和关闭时对激光光强变化的影响, 建立了光伏探测器在波段内连续激光辐照下的解析模型, 模型计算结果与实验结果吻合得较好. 研究表明, 激光辐照过程中的非线性响应, 主要由温度对p-n结内建电场的影响决定, 激光开启和关闭时的开路电压的幅值是由光强和温度共同决定.     

Chaos in photovoltaic HgCdTe detectors under laser irradiation

Chaos in photovoltaic HgCdTe detectors irradiated by a low-power stable continuous-wave laser is found in our experiment. The detectors give a chaotic output in the laser irradiation power density range a little higher than their saturation threshold. Chaos is diagnosed by calculating the power spectrum and the Lyapunov exponent with experimental data of the detectors’ output signals vs. time. We conclude with a qualitative discussion of the possible causes of the observed chaotic behavior. Received: 3 April 2002 / Revised version: 8 July 2002 / Published online: 25 October 2002 RID="*" ID="*"Corresponding author. (Fax: +86-0731/4514127, E-mail: maliqin01@263.net)     

Heterostructure infrared photovoltaic detectors

HgCdTe remains the most important material for infrared (IR) photodetectors despite numerous attempts to replace it with alternative materials such as closely related mercury alloys (HgZnTe, HgMnTe), Schottky barriers on silicon, SiGe heterojunctions, GaAs/AlGaAs multiple quantum wells, InAs/GaInSb strained layer superlattices, high temperature superconductors and especially two types of thermal detectors: pyroelectric detectors and silicon bolometers. It is interesting, however, that none of these competitors can compete in terms of fundamental properties. In addition, HgCdTe exhibits nearly constant lattice parameter which is of extreme importance for new devices based on complex heterostructures. The development of sophisticated controllable vapour phase epitaxial growth methods, such as MBE and MOCVD, has allowed fabrication of almost ideally designed heterojunction photodiodes. In this paper, examples of novel devices based on heterostructures operating in the long wavelength, middle wavelength and short wavelength spectral ranges are presented. Recently, more interest has been focused on p–n junction heterostructures. As infrared technology continues to advance, there is a growing demand for multispectral detectors for advanced IR systems with better target discrimination and identification. HgCdTe heterojunction detectors offer wavelength flexibility from medium wavelength to very long wavelength and multicolour capability in these regions. Recent progress in two-colour HgCdTe detectors is also reviewed.     

连续波激光辐照PV型HgCdTe探测器的新效应

用连续波DF激光辐照PV型HgCdTe红外探测器,得到不同辐照功率密度下,探测器响应输出的一系列实验结果,观察到器件饱和以外的如探测器混沌、探测器单极化等一些新现象,这些结果与理论预期有着较大差别。给出了实验结果的初步解释,该实验结果为今后更好地研究PV型HgCdTe探测器提供了新的线索。     

连续波激光辐照PV型HgCdTe探测器的新效应

 用连续波DF激光辐照PV型HgCdTe红外探测器，得到不同辐照功率密度下，探测器响应输出的一系列实验结果，观察到器件饱和以外的如探测器混沌、探测器单极化等一些新现象，这些结果与理论预期有着较大差别。给出了实验结果的初步解释，该实验结果为今后更好地研究PV型HgCdTe探测器提供了新的线索。     

PV型HgCdTe光电探测器中的混沌及其诊断

对激光辐照半导体光电探测器的实验研究,发现当一束不太强的稳定连续波激光照射在PV型HgCdTe光电探测器上时,可以引起探测器出现混沌行为。利用光电探测器的光电压信号随时间变化的实验数据,通过求功率谱、计算Lyapunov指数对混沌进行了诊断。     

Numerical analysis of two-color HgCdTe infrared photovoltaic heterostructure detector

We report on 2D numerical simulations of spectral photoresponse characteristic for two-color HgCdTe infrared photovoltaic detector. Effects of thickness of absorption layer and doping profiles on the photoresponse, quantum efficiency and crosstalk have been investigated. Optimal thickness of absorption layers and doping profiles are numerically calculated.     

PV型HgCdTe光电探测器中的混沌及其诊断

 对激光辐照半导体光电探测器的实验研究，发现当一束不太强的稳定连续波激光照射在PV型HgCdTe光电探测器上时，可以引起探测器出现混沌行为。利用光电探测器的光电压信号随时间变化的实验数据，通过求功率谱、计算Lyapunov指数对混沌进行了诊断。     

Dependence of transient photovoltage characteristics on bias light intensity for HgCdTe-based photovoltaic infrared detector pixel arrays

In this paper, experimental investigation of the photovoltaic effect of metal/semiconductor (M/S) interface in HgCdTe pixel arrays are reported. The transient photovoltaic (TPV) response was measured by using a pulsed laser under illumination of steady bias light. A tendency of polarity inversion from peak-to-valley of TPV was observed with increasing bias light intensity. Model for photovoltage transformation was proposed, and proved by comparing the response behavior before and after removing the aperture for the TPV measurements. The Schottky barrier junction of M/S interface is the key factor for the polarity reversal at different bias light intensity. The results provide an effective method to evaluate the electrode quality of the photodetector directly.     

描述光伏效应的新解析模型

 对陆启生等人提出的描述光伏效应的解析模型涉及的边界条件进行了讨论，提出了一个适用性更宽的解析模型。通过对新模型、陆的模型以及另一个解析模型的比较，对前两个模型能够描述光伏型光电探测器在强光辐照时的信号饱和效应的原因进行了解释。     

Assessment of HgCdTe photodiodes and quantum well infrared photoconductors for long wavelength focal plane arrays

Recent trends in infrared detectors are towards large, electronically addressed two-dimensional arrays. In the long wavelength infrared (LWIR) spectral range HgCdTe focal plane arrays (FPAs) occupy a dominant position. However, the slow progress in the development of large LWIR photovoltaic HgCdTe infrared imaging arrays and the rapid achievements of novel semiconductor heterostructure systems have made it necessary to foresee the future development of different material technologies in fabrication large FPAs. Among the competing technologies in LWIR are the quantum well infrared photoconductors (QWIPs) based on lattice matched GaAs/AlGaAs and strained layer InGaAs/AlGaAs material systems. This paper compares the technical merits of two IR detector arrays technologies; photovoltaic HgCdTe and QWIPs. It is clearly shown that LWIR QWIP cannot compete with HgCdTe photodiode as the single device especially at higher temperature operation (>70 K) due to fundamental limitations associated with intersubband transitions. However, the advantage of HgCdTe is less distinct in temperature range below 50 K due to problems involved in HgCdTe material (p-type doping, Shockley–Read recombination, trap-assisted tunnelling, surface and interface instabilities). Even though the QWIP is a photoconductor, several of its properties such as high impedance, fast response time, long integration time, and low power consumption, well satisfy the requirements of fabrication of large FPAs. Due to the high material quality at low temperature, QWIP has potential advantages over HgCdTe for very LWIR (VLWIR) FPA applications in terms of the array size, uniformity, yield and cost of the systems.     

描述光伏效应的新解析模型

对陆启生等人提出的描述光伏效应的解析模型涉及的边界条件进行了讨论,提出了一个适用性更宽的解析模型。通过对新模型、陆的模型以及另一个解析模型的比较,对前两个模型能够描述光伏型光电探测器在强光辐照时的信号饱和效应的原因进行了解释。     

PV型HgCdTe线阵探测器对强光反常响应机制研究

采用多种波段内激光辐照带有电容反馈互导放大器(CTIA)读出电路的PV型线阵HgCdTe探测器,实验均发现,当激光功率密度增强到约10-2 W/cm2时,未辐照像素也存在响应,且其基底信号出现以前未曾发现的反常响应,即随功率密度的增加,未辐照像素基底信号的响应值先下降后上升,并且噪声增大。针对这一反常响应现象进行了深入研究,结果表明器件内部公共P级结构、电路共用Vref电压结构是导致这一反常响应的主要原因。     

波段外激光辐照PC型探测器的反常响应机制

 提出了PC型半导体探测器对波段外激光辐照的热电子光电导响应机制。响应波段外激光辐照PC型半导体探测器时,探测器有响应且输出电压信号迅速增大,与波段内激光辐照时的响应规律截然不同,这是由光激发能带内热电子而引起的光电导现象。当较强功率的激光辐照时还应考虑热效应。依据该机制进行了模拟计算,计算结果表明当PC型HgCdTe探测器被波段外激光辐照时,热电子的产生使得电导率减小,进而导致探测器的电阻增大。     

波段外激光辐照PC型探测器的反常响应机制

提出了PC型半导体探测器对波段外激光辐照的热电子光电导响应机制。响应波段外激光辐照PC型半导体探测器时,探测器有响应且输出电压信号迅速增大,与波段内激光辐照时的响应规律截然不同,这是由光激发能带内热电子而引起的光电导现象。当较强功率的激光辐照时还应考虑热效应。依据该机制进行了模拟计算,计算结果表明当PC型HgCdTe探测器被波段外激光辐照时,热电子的产生使得电导率减小,进而导致探测器的电阻增大。     

中波HgCdTe双色红外探测器优化模拟计算

针对光伏型中波HgCdTe双色红外探测器作了优化模拟计算，器件采用典型n-p-p-p-n结构和同时工作模式，建立的二维模型考虑了辐射复合、俄歇复合和Shockley-Read-Hall(SRH)复合三种复合机理，以及深能级辅助隧穿和带间直接隧穿效应，载流子穿过阻挡层势垒的隧道效应采用传递矩阵法计算.分析了双色器件光谱响应随吸收区SRH复合少子(电子)寿命的变化关系，以及串音与阻挡层组分的关系.模拟结果显示，随吸收区少子寿命变短，量子效率迅速下降；为了使器件有较高的量子效率，HgCdTe材料的SRH复合电子寿命应该至少在10ns以上.随阻挡层组分增大，势垒增高，串音迅速减小，大约在阻挡层组分差为0.03时下降到光学串音决定的稳定值，得出了抑制电学串音，阻挡层组分差的临界值为0.03. 关键词： HgCdTe中波双色红外探测器 光谱响应 光谱串音 少子寿命