Hg1—xCdxTe表面电子的子能带结构

讨论了Hg_(1-x)Cd_xTe MIS结构N型反型层电子子能带结构的理论和实验研究结果。描述了采用电容-电压谱,回旋共振谱和磁导振荡谱定量地研究电子子能带结构的模型和方法。推导得到的子能带色散关系,朗道能级和有效g~*因子,与测得的子能带电子的回旋共振和自旋共振结果符合得很好,从而可以定量地研究由于表面电子的自旋轨道相互作用引起的零场分裂效应,朗道能级的移动、交叉,波函数的混合效应以及电致自旋分裂的色散关系。     

P型Hg0.76Cd0.24Te的子能带结构

制备了Ｈｇ１－ｘＣｄｘＴｅ（ｘ＝０．２４）ＭＩＳ器件，用自制的高精度差分电容谱仪测量了器件的Ｃ－Ｖ谱。根据褚君浩等提出的实验模型拟合测得的电容谱，获得了反型层电子子能带结构、，与本文的修正变分自洽方法计算结果基本一致。并获得了有关界面态与绝缘层固定电荷的结果。     

HgCdTe的反常高电子迁移率

文中报道了碲镉汞的反常高电子迁移率。变磁霍尔测量和小光点扫描红外透射测量结果表明，反常高电子迁移率碲镉汞样品中存在导电非均匀性，这种导电非均匀性是横向组分严重偏析形成的负径向电子浓度梯度（电子浓度从晶片中心向周边减小）造成的。负径向电子浓度梯度的导电非均匀性使HgCdTe电子迁移率的测量值反常地高。     

HgCdTe长波光电二极管列阵的等离子体修饰

报道了HgCdTe长波离子注入n+-on-p型光电二极管列阵低能氢等离子体修饰的研究成果.基于采用分子束外延(MBE)技术生长的HgCdTe/CdTe薄膜材料,通过注入窗口的光刻与选择性腐蚀、注入阻挡层的生长、形成光电二极管的B+注入、光电二极管列阵的低能氢等离子体修饰、金属化和铟柱列阵的制备等工艺,得到了氢等离子体修饰的n+-on-p型HgCdTe长波光电二极管列阵.从温度为78 K的电流与电压(I-V)和动态阻抗与电压(R-V)特性曲线中,发现经过低能氢等离子体修饰的HgCdTe红外长波光电二极管列阵动态阻抗极大值比未经过修饰处理的提高了1～2倍,并在反向偏压大于动态阻抗极大值所处的偏压时动态阻抗得到更为明显的提升.这表明低能氢等离子体修饰可以抑制HgCdTe光电二极管列阵暗电流中的带带直接隧穿电流Ibbt和缺陷辅助隧穿电流Itat,从而能提高长波红外焦平面探测器工作的动态范围和探测性能的均匀性.     

Au掺杂碲镉汞长波探测器技术研究

昆明物理研究所多年来持续开展了对Au掺杂碲镉汞材料、器件结构设计、可重复的工艺开发等研究,突破了Au掺杂碲镉汞材料电学可控掺杂、器件暗电流控制等关键技术,将n-on-p型碲镉汞长波器件品质因子(R₀A)从31.3Ω·cm²提升到了363Ω·cm²(λcutoff=10.5μm@80 K),器件暗电流较本征汞空位n-on-p型器件降低了一个数量级以上。研制的非本征Au掺杂长波探测器经历了超过7年的时间贮存,性能无明显变化,显示了良好的长期稳定性。基于Au掺杂碲镉汞探测器技术,昆明物理研究所实现了256×256 (30μm pitch)、640×512 (25μm pitch)、640×512 (15μm pitch)、1 024×768 (10μm pitch)等规格的长波探测器研制和批量能力,实现了非本征Au掺杂长波碲镉汞器件系列化发展。     

金掺杂碲镉汞红外探测材料及器件技术

采用金掺杂替代作为深能级缺陷中心的汞空位,可明显提高P型碲镉汞材料少子寿命,进而降低以金掺杂P型材料为吸收层n-on-p型碲镉汞器件的暗电流,明显提升了n-on-p型碲镉汞器件性能,是目前高灵敏度、高分辨率等高性能n-on-p型长波/甚长波以及高工作温度中波碲镉汞器件研制的一种技术路线选择.本文在分析评述金掺杂碲镉汞材...     

碲镉系导带电子回旋共振线形分析

用远红外激光磁光光谱实验系统测量了Ｎ型碲镉汞的导带电子回旋共振，记录了远红外激光入射下的高分辨回旋共振线形．计算表明，这些线形的特征及其与一些物理量的关系可用经典的Ｄｒｕｄｅ－模型很好地描述．此外，还用理论与实验拟合的方法获得了载流子弛豫时间τ，并与由弱场低频下迁移率得出的弛豫时间τ作了比较，对两者差别的理论问题作了讨论．     

影响碲镉汞晶体电子迁移率的主要因素

通过把迁移率的实测值与影响ＨｇＣｄＴｅ晶体电子迁移率的主要散射机构进行对比，得出结论：位错是ＨｇＣｄＴｅ晶体低温电子迁移率降低的主要原因。     

GaAs／AlGaAs异质结中二维电子气的回旋共振研究

采用栅压比谱的方法，研究了ＧａＡｓ／ＡｌＧａＡｓ异质结中二维电子气（２ＤＥＧ）的回旋共振。观察到由于子能带－朗道能级耦合所引起的回旋共振峰强度随磁场的振荡行为．由回旋共振频率ωｃ确定了子能带电子的回旋共振有效质量ｍ＊，通过对共振峰线形的拟合，获得二维电子气浓度Ｎｓ、电子散射时间τ和迁移率μ．由子能带－朗道能级的共振耦合测量了不同栅压下的多个子能带间的能量间距．讨论了导带非线抛物性对电子回旋共振有效质量的影响     

Comparing ICP and ECR Etching of HgCdTe,CdZnTe, and CdTe

The surface roughness of inductively coupled plasma (ICP)-etched CdTe is greater than that of electron cyclotron resonance (ECR)-etched CdTe. This greater roughness is undesirable for further processing of the material. Lower-frequency plasma excitation from the ICP is more efficient at cracking hydrogen than the high-frequency plasma excitation of ECR. In binary semiconductors it is important to balance removal of both constituents. Bombardment controls the removal of the metal constituent while hydrogen removes the tellurium. Research performed with ECR plasma processing on HgCdTe shows that reducing the pressure can greatly reduce hydrogen ionization. Applying this to ICP it can be shown that reduced pressure greatly improves the morphology of CdTe. This balanced etching also greatly improves etch rate and selectivity of HgCdTe.     

Examination of the effects of high-density plasmas on the surface of HgCdTe

High-density argon-hydrogen plasmas have been demonstrated to be very effective as etchants of CdTe, CdZnTe, and HgCdTe materials for focal plane array applications. Understanding the physical, chemical, and electrical characteristics of these surfaces is critical in elucidating the mechanisms of processing Hg_1−xCd_xTe. The ways in which these plasmas interact with HgCdTe, such as etch rates and loading, have been studied.^1–11 However, little is known on how these plasmas affect the first few atomic layers of HgCdTe. In this study, the effects of high-density plasmas on the surface of HgCdTe were examined. The combination of argon and hydrogen plasma etch leaves a well-ordered, near-stoichiometric surface determined by both x-ray photoelectron spectroscopy and reflection high-energy electron diffraction (RHEED). Starting with Hg_0.78Cd_0.22Te, we were able to produce surfaces with x=0.4 and a RHEED pattern sharp enough to measure 2×1 reconstruction.     

1 MeV电子辐照对碲镉汞中波光导器件的影响

研究了1MeV电子辐照对中波碲镉汞光导器件的影响．通过测试辐照前后光导器件的室温和低温体电阻、响应光谱、电流响应率和探测率等性能参数,结果发现经过电子辐照,器件的峰值和截止波长在辐照后向短波方向移动．在辐照剂量大于10^15／cm^2时,器件的室温电阻和响应率明显下降．探测率由于噪声的影响无明显变化趋势．     

NONDESTRUCTIVE BAND—GAP PROFILE DETERMINATION OF HgCdTe LPE CROWN LAYERS

ＩｎｔｒｏｄｕｃｔｉｏｎＭｏｓｔｏｆｍｏｄｅｒｎＨｇ1-ｘＣｄｘＴｅｔｅｒｎａｒｙｃｏｍｐｏｕｎｄＩＲｐｈｏｔｏｄｅｔｅｃｔｏｒｓａｒｅｍａｎｕｆａｃｔｕｒｅｄｆｒｏｍＬＰＥｆｉｌｍｓｇｒｏｗｎｏｎＣｄＴｅａｎｄＣｄＺｎＴｅｓｕｂｓｔｒａｔｅｓ[1～ 4 ] .Ｃｏｍｐｏ ｓｉｔｉｏｎａｌｄｅｐｔｈｎｏｎｕｎｉｆｏｒｍｉｔｙｓｅｅｍｓｔｏｂｅａｎｉｎｈｅｒｅｎｔｆｅａｔｕｒｅｏｆｔｈｅｓｅｆｉｌｍｓ[5,6 ] .Ｉｔｃａｕｓｅｓｔｈｅｖａｒｉａｔｉｏｎｓｏｆｂａｎｄ ｇａｐｗｉｔｈｔｈｅｄｅｐｔｈ ,ｔｈｕｓａｆｆ…     

高迁移率GaAs/Al0.35Ga0.65As二维电子气的微波回旋共振研究

掌握微波辐照下的电子态性质是理解高迁移率二维电子气在低磁场区的纵向电阻振荡和零电阻态等新奇物理现象的关键.基于反射率测量的微波回旋共振技术(RODCR),研究了高迁移率、低浓度GaAs/Al0.35Ga0.65As二维电子气在Ka波段微波辐照下的电子态性质.通过在不同条件下的RODCR测量,具体讨论了微波交变电场方向、入射激光波长和温度等因素对RODCR测量结果的影响规律.研究结果表明,RODCR测量技术为研究二维电子系统的电子态性质提供了简便而有力的手段.     

High-Performance LWIR MBE-Grown HgCdTe/Si Focal Plane Arrays

We have been actively pursuing the development of long-wavelength infrared (LWIR) HgCdTe grown by molecular beam epitaxy (MBE) on large-area silicon substrates. The current effort is focused on extending HgCdTe/Si technology to longer wavelengths and lower temperatures. The use of Si versus bulk CdZnTe substrates is being pursued due to the inherent advantages of Si, which include available wafer sizes (as large as 300 mm), lower cost (both for the substrates and number of die per wafer), compatibility with semiconductor processing equipment, and the match of the coefficient of thermal expansion with silicon read-out integrated circuit (ROIC). Raytheon has already demonstrated low-defect, high-quality MBE-grown HgCdTe/Si as large as 150 mm in diameter. The focal plane arrays (FPAs) presented in this paper were grown on 100 mm diameter (211)Si substrates in a Riber Epineat system. The basic device structure is an MBE-grown p-on-n heterojunction device. Growth begins with a CdTe/ZnTe buffer layer followed by the HgCdTe active device layers; the entire growth process is performed in␣situ to maintain clean interfaces between the various layers. In this experiment the cutoff wavelengths were varied from 10.0 μm to 10.7 μm at 78 K. Detectors with >50% quantum efficiency and R ₀ A ∼1000 Ohms cm² were obtained, with 256 × 256, 30 μm focal plane arrays from these detectors demonstrating response operabilities >99%. Work supported by the Missile Defense Agency (MDA) through CACI Technologies, Inc. subcontract no. 601-05-0088, NVESD technical task order no. TTO-01, prime contract no. DAAB07-03-D-C214, (delivery order no. 0016)     

HgCdTe detectors operating above 200 K

This paper reports progress with work aimed at using HgCdTe detector arrays at temperatures above 200 K where cooling is possible with thermo-electric coolers. Both theoretical analysis and calculations based on the detector dark currents indicate that useful performance should be obtainable in this temperature range. However, measurements on the performance of two-dimensional arrays show that the thermal sensitivity degrades rapidly for temperatures above 200 K. The reduction in performance at higher temperatures is shown to be mainly due to increasing 1/f noise as the temperature increases. The noise is characterized as a function of bias and temperature and this is used to predict the noise equivalent temperature difference (NETD) as a function of temperature. We describe an approach for producing two-dimensional arrays based on biasing the detector elements at close to zero bias so that the 1/f noise is minimized. A camera based on this concept is described and an example of the imaging performance is shown.     

Macro-loading effects of electron-cyclotron resonance etched II–VI materials

It has been observed in semiconductor processing that the etch rates for materials subjected to an electron-cyclotron resonance (ECR) plasma change with the total sample area. This phenomenon is known as loading. Loading effects can result in pattern definition errors during micromachining. In argon/hydrogen plasmas, designed to etch II–VI materials, loading appears to primarily affect photoresist deterioration. Using an 80% argon-20% hydrogen gas chemistry optimized for HgCdTe, we observe a factor of 2 variation in photoresist etch rate. Loading may also affect semiconductor etch rates to a lesser extent. The observed trends suggest that radical changes in the plasma are the likely cause of this phenomenon.     

The effect of electron cyclotron resonance plasma parameters on the aspect ratio of trenches in HgCdTe

Values of the aspect ratio for trenches etched into HgCdTe by an electron cyclotron resonance (ECR) plasma containing hydrogen and argon are limited by the phenomenon of etch lag. Modeling this plasma as an ion assisted, reactive-etching process leads to a set of conditions that greatly reduces etch lag. Use of these new process conditions produces trenches with aspect ratios greater than 3, widths less than 3 μm, and depths in excess of 15 μm.