硅基HgCdTe光伏器件的暗电流特性分析

对硅基HgCdTe中波器件进行了变温电流电压特性的测试和分析。测量温度从30K到240K,得到R0对数与温度的1000／T的实验曲线及拟合结果。同时选取60K、80K及110K下动态阻抗R与电压V的曲线进行拟合分析。研究表明在我们器件工作的温度点80K,零偏压附近主要的电流机制是产生复合电流和陷阱辅助隧穿电流。要提高器件的水平,必须降低陷阱辅助隧穿电流和产生复合电流对暗电流的贡献。     

硅基HgCdTe光伏器件的暗电流特性分析

对硅基HgCdTe中波器件进行了变温电流电压特性的测试和分析.测量温度从30K到240K,得到R0对数与温度的1000/T的实验曲线及拟合结果.同时选取60K、80K及110K下动态阻抗R与电压V的曲线进行拟合分析.研究表明在我们器件工作的温度点80K,零偏压附近主要的电流机制是产生复合电流和陷阱辅助隧穿电流.要提高器件的水平,必须降低陷阱辅助隧穿电流和产生复合电流对暗电流的贡献.     

不同钝化结构的HgCdTe光伏探测器暗电流机制

在同一HgCdTe晶片上制备了单层ZnS钝化和双层(CdTe+ZnS)钝化的两种光伏探测器,对器件的性能进行了测试,发现双层钝化的器件具有较好的性能.通过理论计算,分析了器件的暗电流机制,发现单层钝化具有较高的表面隧道电流.通过高分辨X射线衍射中的倒易点阵技术研究了单双层钝化对HgCdTe外延层晶格完整性的影响,发现单层ZnS钝化的HgCdTe外延层产生了大量缺陷,而这些缺陷正是单层钝化器件具有较高表面隧道电流的原因.     

不同钝化结构的HgCdTe光伏探测器暗电流机制

在同一HgCdTe晶片上制备了单层ZnS钝化和双层（CdTe+ZnS）钝化的两种光伏探测器,对器件的性能进行了测试,发现双层钝化的器件具有较好的性能．通过理论计算,分析了器件的暗电流机制,发现单层钝化具有较高的表面隧道电流．通过高分辨X射线衍射中的倒易点阵技术研究了单双层钝化对HgCdTe外延层晶格完整性的影响,发现单层ZnS钝化的HgCdTe外延层产生了大量缺陷,而这些缺陷正是单层钝化器件具有较高表面隧道电流的原因．     

MMVCX光伏型HgCdTe中波探测器暗电流温度特性

研究了光伏型HgCdTe中波探测器的暗电流与烘烤时间的关系特性.编写了一种适用于n-on-p型的中波HgCdTe红外探测器的解析拟合程序.结合暗电流的主导机制有扩散机制、产生复合机制、带间直接隧穿机制和陷阱辅助隧穿机制.通过对样品不同烘烤时间的R-V曲线的解析拟合,得到了它们的暗电流成分,提取了6个特征参数.通过对比不同烘烤时间特征参数的变化,分析了烘烤对器件的影响.     

长波HgCdTe光伏器件漏电机理分析

从器件制造工艺的角度，分析了长波ＨｇＣｄＴｅ光伏探测器的体内和表面漏电机理，认为深能级的辅助跃迁在体内漏电方面起主要作用。选择适当的离子注入剂量，可有效地降低体内深能级密度。表面漏电则与ＨｇＣｄＴｅ的表百状态有关，ＺｎＳ／ＨｇＣｄＴｅ之间的界面状态与ＨｇＣｄＴｅ表面的预处理方法有直接关系。控制ＺｕＳ／ＨｇＣｄＴｅ界面组成元素组分，便能控制表面状态，减小表面漏电。经采取相应工艺措施，ｎ＋ｐ结的特性明显提高，单片测量平均零偏阻抗Ｒ０～１０５Ω，平均器件优质Ｒ０Ａ～１Ωｃｍ２。     

Si基HgCdTe材料的电学特性研究

文章研究了Si基分子束外延HgCdTe原生材料、P型退火材料和N型退火材料的霍耳参数、少子寿命等材料电学特性。研究发现，晶格失配导致Si基HgCdTe材料原生材料和N型退火材料迁移率低；Si基原生HgCdTe材料属于高补偿材料，但高补偿性并非材料的固有特性，通过P型退火可使材料变为低补偿材料，迁移率得到提高。采用分子束外延方法制备的3in Si基HgCdTe材料电学性能与GaAs基HgCdTe材料相比，性能还有待提高。改进分子束外延生长工艺提高HgCdTe质量，从而进一步提高迁移率，是Si基外延研究的关键。     

HgCdTe光伏探测器反偏暗电流机制分析

HgCdTe光伏探测器在第二代和第三代红外探测器中处于主流地位.如何降低探测器的暗电流直接关系到探测器的噪声和灵敏度,其分析计算方法有多种.运用Synopsys半导体器件模拟软件对HgCdTepn结各种机制下的反偏暗电流和动态微分电阻进行了模拟计算.计算结果和相关文献报道的结果以及试验测试结果都吻合很好.     

改进器件工艺降低硅光电探测器暗电流

为降低硅光电探测器ｐ－ｎ结反向暗电流，可在器件制作工艺中采用一系列完美晶体器件工艺ＰＣＤＴ。在实施过程中，作者对吸除工艺，应力补偿工作等作了改进，进一步降低了反向暗电流。     

硅基HgCdTe面阵焦平面器件结构热应力分析

红外焦平面器件是一个多层结构,包含外延衬底、HgCdTe芯片、Si读出电路、互连In柱、粘结胶以及引线基板等,由于各层材料之间的热膨胀系数不同导致焦平面器件在工作中承受很大的热应力,热应力是导致红外焦平面器件失效的重要因素之一。本文运用一维模型以及有限元分析方法对硅基HgCdTe320×240焦平面器件结构进行热应力分析,结果表明,改变Si衬底厚度、粘结胶的杨氏模量以及基板的热膨胀系数,都会不同程度地影响HgCdTe薄膜上的受力,其中基板的热膨胀系数对HgCdTe薄膜所受的应力影响最大。通过选用合适的基板可以有效降低HgCdTe薄膜所受的应力,从而降低器件失效率。     

High-Operating-Temperature HgCdTe Avalanche Photodiodes

In this communication we report the first results of electro-optical characterization of planar heterostructure HgCdTe avalanche photodiodes (APDs), which enables the operation of APDs at high gain, at low bias, and with low dark current and/or at high operating temperature (HOT). The APD is based on a heterostructure in which the photons are detected in a wide-band-gap layer, and the photoelectrons are amplified in a vertical junction in a confined narrow-gap layer. The dark diffusion current and thermal background sensitivity of the device are limited by using a thin narrow-band-gap amplification layer. In addition, the defect-limited dark current is also expected to be reduced due to the reduced volume of the narrow-band-gap depletion layer. The electro-optical performance was characterized at T = 80 K and T = 200 K for two devices with a nominal thickness of the amplification layer of w = 100 nm and 500 nm, realized in x _Cd = 0.3 Hg-vacancy-doped layers grown by molecular-beam epitaxy (MBE). The measurements show an average gain of 〈M〈 = 10 at a reverse bias of 5 V, which is slightly reduced compared with a conventional APD with x _Cd = 0.3. The thermal diffusion current measured at low reverse bias, V _b = 0.1 V, and at T = 200 K is about 0.1 mA/cm² to 0.3 mA/cm², which is a factor of 50 lower than standard x _Cd = 0.3 n-on-p APDs. The quantum efficiency due to absorption in the gain layer is high (QE_peak > 30%), although no antireflecting coating was used, indicating that the device can also be used for high-operating-temperature thermal detection.     

Gain and Dark Current Characteristics of Planar HgCdTe Avalanche Photo Diodes

HgCdTe midwave infrared pin avalanche photodiodes (APDs) have been studied as a function of temperature and bias, for two types of junction profiles with different nominal junction width and the same cut-off wavelength λc = 5.0 μm at T = 77 K. A gain of 5,300 at a reverse bias of 12.5 V was demonstrated in the nominally wide junction pin-APD at T = 77 K. The nominally narrow pin-APD showed a higher gain at low bias, but the maximum gain was lower due to an earlier onset of excess currents. The gain was measured for temperatures (T) between 30 K and 150 K and was found to decrease with increasing temperatures, in correlation with the increase in band gap. However, the useful gain was reduced at lower temperatures, due to increased excess current at high reverse bias, indicating a tunnel limited origin of the sensitivity limiting excess current. The noise factor, F, showed a nearly deterministic multiplication of the carriers, with F = 1–1.5 up to gains of 5,000.     

Analysis of 1/f noise in LWIR HgCdTe photodiodes

We study the 1/f noise currents and dark currents in LWIR HgCdTe photodiodes. The measured dark currents of the diodes processed by post implantation annealing with different annealing times are analyzed using current model fitting methods. The different dark current components, such as diffusion current, generation-recombination current, band-to-band tunneling current, and trap assisted tunneling current, at various bias voltages can be separated from the measured dark currents. By the fitting analysis, some physical parameters are extracted and different annealing effects can be explained by the parameters. The improvements in diode characteristics by post implantation annealing can be explained by the changes of trap density, donor concentration, minority carrier lifetime, and generation lifetime. The 1/f noise currents are measured over a wide range of reverse bias voltages, and correlated with the extracted dark currents by superposition of the noise generated by the different dark current mechanisms. It turns out that the band-to-band tunneling has a smaller correlation with the 1/f noise than other current components, and the trap center seems to be responsible for the 1/f noise characteristics of the LWIR HgCdTe photodiodes.     

Characterization of HgCdTe MWIR Back-Illuminated Electron-Initiated Avalanche Photodiodes

This article reports new characterization data for large-area (250 μm ×  250 μm) back-illuminated planar n-on-p HgCdTe electron-initiated avalanche photodiodes (e-APDs). These e-APDs were fabricated in p-type HgCdTe films grown by liquid-phase epitaxy (LPE) on CdZnTe substrates. We previously reported that these arrays exhibit gain that increases exponentially with reverse bias voltage, with gain-versus-bias curves that are quite uniform from element to element, and with a maximum gain of 648 at −11.7 V at 160 K for a cutoff wavelength of 4.06 μm. Here we report new data on these planar e-APDs. Data from a third LPE film with a longer cutoff wavelength (4.29 μm at 160 K) supports the exponential dependence of gain on cutoff wavelength, for the same bias voltage, that we reported for the first two films (with cutoffs of 3.54 μm and 4.06 μm at 160 K), in agreement with Beck’s empirical model for gain versus voltage and cutoff wavelength in HgCdTe e-APDs. Our lowest gain-normalized current density at 80 K and zero field-of-view is 0.3 μA/cm² at −10.0 V for a cutoff of 4.23 μm at 80 K. We report data for the temperature dependence of gain over 80 K to 200 K. We report, for the first time, the dependence of measured gain on junction area for widely spaced circular diodes with radii of 20 μm to 175 μm. We interpret the variation of measured gain with junction area in terms of an edge-enhanced electric field, and fit the data with a two-gain model having a lower interior gain and a higher edge gain. We report data for the excess noise factor F(M) near unity for gains up to 150 at 196 K. We describe the abrupt breakdown phenomenon seen in most of our devices at high reverse bias.     

论碲镉汞光电二极管的暗电流(下)

对于工作在1～30 μm波段的各种红外光电探测器来说,碲镉汞(MercuryCadmium Telluride,MCT)已经成为最重要的一种半导体材料.为了获得最优的性能,MCT探测器的暗电流必须降至最小.主要根据近年来的部分英文文献,从基本概念入手,介绍了有关MCT光电二极管暗电流研究的发展情况,并讨论了对于MCT光电二极管暗电流有关问题的理解和体会.     

Si基大面积碲镉汞分子束外延研究

文章报道了Si基碲镉汞分子束外延(MBE)的最新研究进展。尝试用晶向偏角降低高界面应变能的方法,摸索大失配体系中位错的抑制途径,寻找位错密度与双晶半峰宽的对应关系,基本建立了外延材料晶体质量无损检测评价标准,并对外延工艺进行指导。通过上述研究,15~20μm Si基CdTe复合材料双晶半峰宽最好结果为54arcsec,对应位错密度(EPD)小于2×106/cm2,与相同厚度的GaAs/CdTe(211)双晶水平相当,达到或优于国际最好结果。获得的3 in 10μm Si基HgCdTe材料双晶半峰宽最好结果为51arcsec,目前Si基HgCdTe材料已经初步应用于焦平面中波320×240器件制备。     

Generation-Recombination Effect in High-Temperature HgCdTe Heterostructure Nonequilibrium Photodiodes

The dark current of near-room-temperature long-wavelength heterojunction photodiodes was studied. The dark current of the devices is much greater than that calculated from the Auger generation mechanisms. A model of trap- assisted tunneling via traps located at dislocation cores is proposed as the mechanism of enhanced thermal generation of charge carriers in reverse-biased diodes. Field-induced reduction of trap activation energies can increase thermal generation and create conditions for tunneling currents. The model qualitatively explains experimental current−voltage characteristics of the diodes assuming a dislocation density of approximately 10⁸ cm⁻² at the graded gap interface between absorber and contact regions of the photodiode.