离子束刻蚀HgCdTe环孔pn结I—V、RD—V特性的研究（上）

本文推导了一种可简便、准确、直观计算和分析pn结I-V特性的公式和方法,并应用该方法对两类典型HgCdTe环孔pn结的I-V、RD-V特性进行了计算和拟合;得到了表面欧姆(反型沟道)漏电导、二极管理想因子n随电压的分布等反映二极管结特性的重要参数.计算结果表明,对于长波HgCdTe光伏器件而言,表面漏电流在整个暗电流中所占的比重相当大,表面漏电流严重地制约着器件性能.HgCdTe材料的晶体缺陷会使二极管的理想因子n增大,从而使产生-复合电流及陷阱辅助隧穿电流增加.     

离子束刻蚀HgCdTe环孔pn结Ⅰ-Ⅴ、RD-Ⅴ特性的研究(下)

本文推导了一种可简便,准确、直观计算和分析pn结Ⅰ-Ⅴ特性的公式和方法,并应用该方法对两类典型HgCdTe环孔pn结的Ⅰ-Ⅴ、RD-Ⅴ特性进行了计算和拟合;得到了表面欧姆(反型沟道)漏电导、二极管理想因子n随电压的分布等反映二极管结特性的重要参数.计算结果表明,对于长波HgCdTe光伏器件而言,表面漏电流在整个暗电流中所占的比重相当大,表面漏电流严重地制约着器件性能.HgCdTe材料的晶体缺陷会使二极管的理想因子n增大,从而使产生-复合电流及陷阱辅助隧穿电流增加.     

离子束刻蚀HgCdTe环孔pn结Ⅰ—Ⅴ、R_D—V特性的研究(下)

本文推导了一种可简便、准确、直观计算和分析pn结Ⅰ-Ⅴ特性的公式和方法,并应用该方法对两类典型HgCdTe环孔pn结的Ⅰ-Ⅴ、R_D-V特性进行了计算和拟合;得到了表面欧姆(反型沟道)漏电导、二极管理想因子n随电压的分布等反映二极管结特性的重要参数。计算结果表明,对于长波HgCdTe光伏器件而言,表面漏电流在整个暗电流中所占的比重相当大,表面漏电流严重地制约着器件性能。HgCdTe材料的晶体缺陷会使二极管的理想因子n增大,从而使产生-复合电流及陷阱辅助隧穿电流增加。     

离子束刻蚀HgCdTe环孔pn结I–V、RD–V特性的研究（下）

本文推导了一种可简便、准确、直观计算和分析pn结I–V特性的公式和方法,并应 用该方法对两类典型HgCdTe环孔pn结的I–V、RD–V特性进行了计算和拟合;得到了表面欧姆(反型沟道)漏 电导、二极管理想因子n随电压的分布等反映二极管结特性的重要参数。计算结果表明,对于长波HgCdTe 光伏器件而言,表面漏电流在整个暗电流中所占的比重相当大,表面漏电流严重地制约着器件性能。HgCdTe 材料的晶体缺陷会使二极管的理想因子n增大,从而使产生–复合电流及陷阱辅助隧穿电流增加。     

离子束刻蚀HgCdTe环孔pn结Ⅰ-Ⅴ、R_D-V特性的研究(上)

本文推导了一种可简便、准确、直观计算和分析pn结Ⅰ-Ⅴ特性的公式和方法,并应用该方法对两类典型HgCdTe环孔pn结的Ⅰ-Ⅴ、R_D-V特性进行了计算和拟合;得到了表面欧姆(反型沟道)漏电导、二极管理想因子n随电压的分布等反映二极管结特性的重要参数。计算结果表明,对于长波HgCdTe光伏器件而言,表面漏电流在整个暗电流中所占的比重相当大,表面漏电流严重地制约着器件性能。HgCdTe材料的晶体缺陷会使二极管的理想因子n增大,从而使产生-复合电流及陷阱辅助隧穿电流增加。     

离子束刻蚀HgCdTe环孔pn结I-V、RD-V特性的研究（下）

本文推导了一种可简便、准确、直观计算和分析pn结I-V特性的公式和方法,并应用该方法对两类典型HgCdTe环孔pn结的I-V、RD—V特性进行了计算和拟合;得到了表面欧姆（反型沟道）漏电导、二极管理想因子n随电压的分布等反映二极管结特性的重要参数。计算结果表明,对于长波HgCdTe光伏器件而言,表面漏电流在整个暗电流中所占的比重相当大,表面漏电流严重地制约着器件性能。HgCdTe材料的晶体缺陷会使二极管的理想因子n增大,从而使产生一复合电流及陷阱辅助隧穿电流增加。     

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.     

红外光电探测器及材料

1.本征光电探测器及材材的现状与展望当前,红外光电材料及器件的研制工作,主要是围绕最终成批生产价格适宜、性能优良的镶嵌焦平面阵列这一中心目标开展的。HgCdTe材料由于光电性能优良和适用谱区宽(1～30μm)而居于首要地位。据估计,在目前红外光电探测器和材料的研制项目中,HgCdTe方面的项目大约占80～90%。至1990年,材料的主要课题在于成批制造成本低、性能优良的大面积(单晶)薄膜。近年来较集中地开展了HgCdTe液相外延工     

HgCdTe混合焦平面阵列

前言近年来,HgCdTe已成为高密度焦平面阵列第二代红外成像系统的重要的半导体材料。为得到所需性能,提出一种采用HgCdTe光电二极管和硅电荷耦合器件的混合焦平面结构。异质结和薄基底二极管结构可保证在3～5微米和8～12微米两个波段制成性能高的器件。因为这两种结构都可大大降低饱和电流密度。本文介绍异质结和薄基底混合阵列的最近发展。     

CdTe/ZnS复合钝化层对长波碲镉汞器件性能的影响研究

采用CdTe/ZnS复合钝化技术对长波HgCdTe薄膜进行表面钝化,并对钝化膜生长工艺进行了改进。采用不同钝化工艺分别制备了MIS器件和二极管器件,并进行了SEM、C-V和I-V表征分析,研究了HgCdTe/钝化层之间的界面特性及其对器件性能的影响。结果表明,钝化工艺改进后所生长的CdTe薄膜更为致密且无大的孔洞,CdTe/HgCdTe界面晶格结构有序度获得改善;采用改进的钝化工艺制备的MIS器件C-V测试曲线呈现高频特性,界面固定电荷面密度从改进前的1.671011 cm-2下降至5.691010 cm-2;采用常规钝化工艺制备的二极管器件在较高反向偏压下出现较大的表面沟道漏电流,新工艺制备的器件表面漏电现象获得了有效抑制。     

HgCdTe long-wavelength infrared photovoltaic detectors fabricated using plasma-induced junction formation technology

A long-wavelength infrared (LWIR) HgCdTe photodiode fabrication process has been developed based on reactive ion etching (RIE) plasma-induced p-to-n type conversion for junction formation. The process has been successfully applied to produce devices using both vacancy-doped and gold-doped liquid phase epitaxy (LPE)-grown p-type HgCdTe material with a cut-off wavelength of 10 μm at 77 K. The fabrication procedure is outlined and results are presented on completed devices that indicate the effect of variations in processing parameters. The fabricated devices have been characterized by measurements of the diode dark I-V characteristic over the temperature range 20–200 K, as well as by spectral responsivity measurements. Analysis of the device I-V data, variable area data, and modeling of diode dark current mechanisms indicates that gold-doped material results in higher performing devices compared to vacancy-doped material. Device performance is found to be strongly affected by trap-assisted tunneling currents and surface leakage currents at zero bias. Nonoptimum surface passivation is likely to be the major factor limiting performance at this early stage of device technology development.     

Planar p-on-n HgCdTe heterojunction mid-wavelength infrared photodiodes formed using plasma-induced junction isolation

Planar p-on-n HgCdTe heterojunction photodiodes have been fabricated using a plasma-induced type conversion process for device junction isolation. The technique is presented as a fully planar alternative technology to the commonly used mesa isolation structure. The starting material consisted of an indium-doped n-type mid-wavelength infrared (MWIR) HgCdTe absorbing layer that was capped by a 1-μm-thick wider bandgap arsenic-doped p-type layer. Junction-isolated p-on-n diodes were formed by selectively p-to-n type converting the p-type cap layer using a plasma process. Photodiode dark current-voltage measurements were performed as a function of temperature, along with noise and responsivity. The devices have cut-off wavelengths between 4.8 μm and 5.0 μm, exhibit diffusion-limited dark currents down to 145 K, give R₀A values greater than 1 × 10⁷Ω·cm² at 80 K and greater than 1 × 10⁵Ω·cm² at 120 K, and have negligible 1/f noise current at zero applied bias.     

HgCdTe negative luminescence devices for cold shielding and other applications

Negative luminescence (NL) refers to the suppression of infrared blackbody emission, and hence an apparent temperature reduction, due to free carrier extraction from a reverse-biased p-n junction. A number of applications are envisioned for NL devices, including cold shielding of background-limited uncooled and cryogenic focal-plane arrays, dynamic nonuniformity correction for ir imaging, and ir scene simulation. High-performance NL devices have recently been demonstrated. For example, a HgCdTe/CdZnTe photodiode with 4.8-μm cutoff wavelength achieved an internal NL efficiency of 95% at room temperature. This means that the blackbody emission was suppressed by a factor of 20 and that the apparent temperature of the device surface decreased by 60 K. The corresponding reverse-bias saturation current density was 0.11 A/cm². Even HgCdTe devices (λ _co=5.3 μm) grown on large-area silicon substrates with substantial lattice mismatch displayed 88% internal NL efficiency and saturation current densities no larger than 1.3 A/cm². These results indicate a clear path toward a negative-luminescence device technology that is efficient, operates at low power, and is inexpensive.     

Progress in MOVPE of HgCdTe for advanced infrared detectors

This paper reviews the significant progress made over the past five years in the development of metalorganic vapor phase epitaxy (MOVPE) for the in situ growth of HgCdTe p-n junction devices for infrared detector arrays. The two basic approaches for MOVPE growth of HgCdTe, the interdiffused multilayer process (IMP), and direct alloy growth (DAG) are compared. The paper then focuses on the progress achieved with the IMP approach on lattice-matched CdZnTe substrates. The benefits of the precursors ethyl iodide (EI) and tris-dimethylaminoarsenic (DMAAs) for controlled iodine donor doping and arsenic acceptor doping at dopant concentrations relevant for HgCdTe junction devices are summarized along with the electrical and lifetime properties of n-type and p-type HgCdTe films grown with these precursors. The relative merits of the two CdZnTe substrate orientations we have used, the (211)B and the (100) with 4°–8° misorientation are compared, and the reasons why the (211)B is preferred are discussed. The growth and repeatability results, based on secondary ion mass spectrometry analysis, are reported for a series of double-heterojunction p-n-N-P dual-band HgCdTe films for simultaneous detection in the 3–5 μm and 8–10 μm wavelength bands. Finally, the device characteristics of MOVPE-IMP in situ grown p-on-n heterojunction detectors operating in the 8–12 μm band are reviewed and compared with state-of-the-art liquid phase epitaxial grown devices.     

碲镉汞p^＋-on-n长波异质结探测器的研究

报道了HgCdTe p^ -on-o长波异质结焦平面器件的研究结果．采用由分子柬外延(MBE)和原位掺杂技术生长的P^ -on-n异质结材料，通过湿法腐蚀、台面钝化、台面金属化、铟柱制备和互连等工艺，得到了HgCdTe p^ -on-o长波异质结焦平面器件．根据，I-V实验结果和暗电流理论，拟合计算和分析了各种暗电流机制对器件性能的影响．且获得了器件的响应光谱和探测率。     

Heteroepitaxy of HgCdTe (211)B on Ge substrates by molecular beam epitaxy for infrared detectors

Epitaxial growth of (211)B CdTe/HgCdTe has been achieved on two inch germanium (Ge) by molecular beam epitaxy (MBE). Germanium was chosen as an alternative substrate to circumvent the weaknesses of CdZnTe wafers. The ease of surface preparation makes Ge an attractive candidate among many other alternative substrates. Best MBE CdTe growth results were obtained on (211) Ge surfaces which were exposed to arsenic and zinc fluxes prior to the MBE growth. This surface preparation enabled CdTe growth with B-face crystallographic polarity necessary for the HgCdTe growth. This process was reproducible, and produced a smooth and mirror-like surface morphology. The best value of the {422} x-ray double diffraction full width at half maximum measured from the HgCdTe layer was 68 arc-s. We present the 486 point maps of FWHM statistical values obtained from CdTe/Ge and HgCdTe/CdTe/Ge. High resolution microscopy electron transmission and secondary ion mass spectroscopy characterization results are also presented in this paper. High-performance middle wavelength infrared HgCdTe 32-element photodiode linear arrays, using the standard LETI/LIR planar n-on-p ion implanted technology, were fabricated on CdTe/Ge substrates. At 78K, photodiodes exhibited very high R₀A figure of merit higher than 10⁶ Ωcm⁻² for a cutoff wavelength of 4.8 μm. Excess low frequency noise was not observed below 150K.     

Small two-dimensional arrays of mid-wavelength infrared HgCdTe diodes fabricated by reactive ion etching-induced p-to-n-type conversion

The reactive ion etching (RIE) technique has been shown to produce high-performance n-on-p junctions by localized-type conversion of p-type mid-wavelength infrared (MWIR) HgCdTe material. This paper presents variable area analysis of n-on-p HgCdTe test diodes and data on two-dimensional (2-D) arrays fabricated by RIE. All devices were fabricated on x = 0.30 to 0.31 liquid-phase epitaxy (LPE) grown p-type (p = ∼1 × 10¹⁶ cm⁻³) HgCdTe wafers obtained from Fermionics Corp. The diameter of the circular test diodes varied from 50 μm to 600 μm. The 8 × 8 arrays comprised of 50 μm × 50 μm devices on a 100-μm pitch, and all devices were passivated with 5000 ? of thermally deposited CdTe. At temperatures >145 K, all devices are diffusion limited; at lower temperatures, generation-recombination (G-R) current dominates. At the lowest measurement temperature (77 K), the onset of tunneling can be observed. At 77 K, the value of 1/R₀A for large devices shows quadratic dependence on the junction perimeter/area ratio (P/A), indicating the effect of surface leakage current at the junction perimeter, and gives an extracted bulk value for R₀A of 2.8 × 10⁷ Ω cm². The 1/R₀A versus P/A at 195 K exhibits the well-known linear dependence that extrapolates to a bulk value for R₀A of 17.5 Ω cm². Measurements at 77 K on the small 8 × 8 test arrays were found to demonstrate very good uniformity with an average R₀A = 1.9 × 10⁶ Ω cm² with 0° field of view and D* = 2.7 × 10¹¹cm Hz^1/2/W with 60° field of view looking at 300 K background.     

High-Operating-Temperature MWIR Detector Diodes

The high-operating-temperature (HOT) midwave infrared (MWIR) n-on-p detector has been pursued using the high-density vertically integrated photodiode (HDVIP^®) architecture. In this device, arsenic-doped HgCdTe grown by liquid-phase epitaxy (LPE) is used, passivated on both surfaces with interdiffused CdTe. Dark current densities on these diodes as low as 2.5 mA/cm² normalized to a 5 μm cutoff at 250 K have been demonstrated. 1/f noise at 1 Hz, measured at 250 K, is found to be 6 × 10^?11 A/rHz-cm measured on a cutoff of 4.43 μm. These results agree with the theoretical predictions for the devices made.     

HgCdTe MWIR Back-Illuminated Electron-Initiated Avalanche Photodiode Arrays

This paper reports data for back-illuminated planar n-on-p HgCdTe electron-initiated avalanche photodiode (e-APD) 4 × 4 arrays with large unit cells (250 × 250 μm²). The arrays were fabricated from p-type HgCdTe films grown by liquid phase epitaxy (LPE) on CdZnTe substrates. The arrays were bump-mounted to fanout boards and characterized in the back-illuminated mode. Gain increased exponentially with reverse bias voltage, and the gain versus bias curves were quite uniform from element to element. The maximum gain measured was 648 at −11.7 V for a cutoff wavelength of 4.06 μm at 160 K. For the same reverse-bias voltage, the gains measured at 160 K for elements with two different cutoff wavelengths (3.54 μm and 4.06 μm at 160 K) show an exponential increase with increasing cutoff wavelength, in agreement with Beck’s empirical model for gain versus voltage and cutoff wavelength in HgCdTe e-APDs. Spot scan data show that both the V = 0 response and the gain at V = −5.0 V are spatially uniform over the large junction area. To the best of our knowledge, these are the first spot scan data for avalanche gain ever reported for HgCdTe e-APDs. Capacitance versus voltage data are consistent with an ideal abrupt junction having a donor concentration equal to the indium concentration in the LPE film. U.S. Workshop on the Physics and Chemistry of II-VI Materials Newport Beach, California October 10–12, 2006.