Cd1-xZnxTe多晶薄膜的制备、性能与光伏应用

用共蒸发法制备了Cd1-xZnxTe多晶薄膜,薄膜结构属立方晶系空间群F43m.通过透射光谱的测量,计算光能隙,得到室温时薄膜的光能隙随组分x值的变化满足二次方关系.作为对异质结界面的修饰,提出了有Cd1-x-ZnxTe过渡层的CdS/CdTe/Cd1-xZnxTe/ZnTe∶Cu电池.并在相同工艺下制备了CdS/CdTe/Cd0.4Zn0.6Te/ZnTe∶Cu与CdS/CdTe/ZnTe∶Cu太阳电池,发现前者比后者效率平均增加了35.0%.     

高阻值Cd1-xZnxTe晶体的生长及其性能测试

通过适当的工艺措施,采用Bridgman法生长了直径为30mm的X射线及γ射线探测器级的Cd0.9Zn0.1Te晶锭.测试结果表明:该晶锭结晶质量良好,位错密度低,成分均匀,杂质含量低,红外透过率和电阻率都十分接近本征Cd0.9Zn0.1Te的值.并从晶体的生长特性、缺陷和杂质的角度,分析了生长高性能晶体的条件,研究了生长Cd1-xZnxTe晶体的x值与缺陷和杂质浓度之间的关系.     

碲锌镉（Cd1-xZnxTe）材料的第一性原理研究

Cd_(1-x)Zn_xTe(CZT)材料具有优良的光敏特性和电学性质,其应用领域或多或少都涉及到材料结构完整性的问题,因此材料结构的优化已经成为亟待解决的重要问题之一。本文简要介绍了借助第一性原理的方法研究CZT材料,通过其电子结构的信息对已有的实验表征、缺陷、掺杂对材料的成键机制、悬挂键的分布及能带结构的影响机制加以验证,从而能够为材料的生长机制和器件设计提供有力的理论依据。     

Cd1-xZnxTe合金的退火研究

用红外透射谱和喇曼散射谱研究了退火对 Cd1 - x Znx Te晶片中 Te沉淀的影响 .研究结果表明 ,红外透射谱只对大尺寸的 Te沉淀较为敏感 ,而喇曼散射谱却能够探测到样品中小尺寸的 Te沉淀 ,两者互为补充 .在 Cd气氛下对晶片进行退火处理 ,选择合适的退火温度和退火时间 ,可以有效地消除晶片中大尺寸的 Te沉淀 ,却难以消除晶片中小尺寸的微量 Te沉淀     

Cd1-xZnxTe合金的退火研究

用红外透射谱和喇曼散射谱研究了退火对Cd1-xZnxTe晶片中Te沉淀的影响．研究结果表明,红外透射谱只对大尺寸的Te沉淀较为敏感,而喇曼散射谱却能够探测到样品中小尺寸的Te沉淀,两者互为补充．在Cd气氛下对晶片进行退火处理,选择合适的退火温度和退火时间,可以有效地消除晶片中大尺寸的Te沉淀,却难以消除晶片中小尺寸的微量Te沉淀．     

Cd_(1-x)Zn_xTe多晶薄膜的制备、性能与光伏应用

用共蒸发法制备了 Cd1 - x Znx Te多晶薄膜 ,薄膜结构属立方晶系空间群 F4 3m.通过透射光谱的测量 ,计算光能隙 ,得到室温时薄膜的光能隙随组分 x值的变化满足二次方关系 .作为对异质结界面的修饰 ,提出了有 Cd1 - x-Znx Te过渡层的 Cd S/ Cd Te/ Cd1 - x Znx Te/ Zn Te∶ Cu电池 .并在相同工艺下制备了 Cd S/ Cd Te/ Cd0 .4 Zn0 .6 Te/ Zn Te∶ Cu与 Cd S/ Cd Te/ Zn Te∶ Cu太阳电池 ,发现前者比后者效率平均增加了 35 .0 % .     

渐变带隙Cd1-xZnxTe太阳电池光电转换效率的数值模拟

Cd1-xZnxTe是直接带隙半导体材料,其禁带宽度随x值的变化在1.45eV～2.26eV间连续可调.将具有渐变带隙结构的材料作为太阳电池的光吸收层,可以在近背表面的薄层内产生一个准电场.该电场不仅能将俄歇复合发生的位置有效局域化,而且还可降低由表面复合引起的载流子损耗,增强光生载流子的收集效率,进而提高电池的光电转换效率.用渐变带隙Cd1-xZnxTe多晶薄膜替代了传统CdTe薄膜太阳电池中的均匀相CdTe光吸收层,并用AMPS软件模拟分析了渐变带隙Cd1-xZnxTe太阳电池的光电响应特性.经计算,该电池在理想情况下(无界面态、有背面场,正背面反射率分别为0和1)的光电转换效率高达41%.     

CoSi合金的磁性和光学性质的第一性原理研究

采用第一性原理的局域自旋密度近似和在位库伦能修正(LSDA+U)的计算方法,结合广义梯度近似下的赝势平面波方法,计算了CoSi合金的磁性和光学性质。计算结果显示在费米能级附近,CoSi合金的上自旋能级与下自旋能级相互交叠,出现了明显的自旋极化现象,并且自旋态密度都穿过费米能级,表明CoSi合金具有金属特征。磁性计算结果表明CoSi合金具有铁磁性,磁性主要来源于Co原子3d轨道电子的贡献。特别是采用LSDA+U修正方法发现,当位库伦修正值增加到6.6eV时,CoSi合金体系的几何参数与实验值完全吻合,表明位库仑能U值的大小对CoSi合金的原子磁矩以及磁性原子的能级分布影响较大。同时,光学吸收谱计算结果表明,随着位库仑能U值的增大,CoSi合金的吸收峰在低能区发生红移,在高能区发生蓝移。以上结果表明,CoSi合金是一种很好的磁光导电材料。     

Ag、P掺杂ZnS的电子结构和光学性质的研究

利用密度泛函理论中的第一性原理计算掺杂Ag、P的ZnS材料,对掺杂Ag、P前后ZnS超晶胞的电子结构以及光学性质进行了分析研究。计算结果表明,掺入杂质后,价带顶出现杂质能级,费米能级进入价带,导致电导率增加,P 3p态电子形成的杂质态具有一定的局域化特性,故P在ZnS中的溶解度比较低,ZnS的光学性质在可见光区有比较明显的变化,而在高能区则比较相似。掺杂后,各谱线在低能区均产生了一个新的峰。     

CdCO_3电子结构与光学属性的第一性原理研究

采用基于密度泛函理论框架的第一性原理计算方法,利用广义梯度近似方法研究了CdCO_3的晶体结构、电子结构和光学属性,理论计算结果表明,CdCO_3属于间接宽带隙半导体材料,带隙宽度为2.59 e V,带隙主要由价带顶的Cd 4p、O 2p和导带底的Cd 4p、5s轨道能级决定的。而电荷密度结果显示CdCO_3晶体是一种离子性较强而共价性较弱的混合键半导体,具有强烈的p轨道与d轨道杂化分布特征。利用精确计算的能带结构和态密度分析了带间跃迁占主导地位的CdCO_3材料的光学属性,光学性质的计算结果显示在0~15 e V的能量范围内出现了三个明显的介电峰,吸收带边对应于紫外波段。以上结果对于探索基于CdCO_3纳米材料的潜在应用具有重要的理论指导意义,也为精确监测和控制CdCO_3材料的生长提供了理论依据。     

Improvement of the accuracy of the In-situ ellipsometric measurements of temperature and alloy composition for MBE grown HgCdTe LWIR/MWIR structures

Spectroscopic ellipsometry (SE) has proven to be a very reliable technique for the in-situ monitoring of the substrate temperature and alloy composition during the HgCdTe epitaxy. In this work, the influence of the variations in the angle of incidence and the spectral wavelength shift on the measured accuracy of the growth temperature and alloy composition are studied, and a method for precisely determining these variations independent of the modeling of the SE data has been developed. It is shown that the stability of the fittings of the optical models for in-situ applications increases and that the couplings between model parameter decreases upon either eliminating the angle of incidence as an independent model parameter or correcting for the shifts of the wavelength offset. The variations in the angle of incidence and wavelength shift, which arise in the M88 ellipsometer from reflected beam deflections, were precisely calibrated in two dimensions as a function of alignment parameters, using a thick thermally grown SiO₂/Si sample and were parameterized for our experimental geometry. A new extension of theWVASE software was developed to correct the raw SE data in real time for wavelength shift and the angle of incidence drift. A comparison of the corrected and uncorrected results of in-situ temperature measurements for HgCdTe and CdZnTe(211) B/Si(211) clearly demonstrates that the proposed method significantly enhances the accuracy of temperature and composition readings over a broad range of values in these parameters.     

Compositional dependence of infrared phonon parameters for Hg1-xCdxTe

The full set of Lorentzian oscillator parameters describing the two-mode phonon behavior in Hg_1-x-jCd_xTe is reported. A new analysis of reflectivity spectra combined with existing results gives the most accurate available values for the CdTe-like and HgTe-like transverse optical frequency, strength and (for the first time) damping constant vs CdTe fractionx at room, liquid nitrogen and liquid helium temperatures. Polynomial fits vsx for each parameter are provided for use in characterizing Hg_1-xCd_xTe and the HgTe-CdTe superlattice.     

Growth and properties of Hg1-x Cdx Te epitaxial layers

The growth of epitaxial layers of mercury-cadmium-telluride (Hg_1-xCd_xTe) with relatively low x (0.2-0.3) from Te-rich solutions in an open tube sliding system is studied. The development of a semiclosed slider system with unique features permits the growth of low x material at atmospheric pressure. The quality of the films is improved by the use of Cd_1-yZ_yTe and Hg_1-xCd_xTe substrates instead of CdTe. The substrate effects and the growth procedure are discussed and a solidus line at a relatively low temperature is reported. The asgrown epitaxial layers are p-type with hole concentration of the order of 1·10¹⁷ cm⁻³, hole mobility of about 300 cm²·V⁻¹ sec⁻¹ and excess minority carrier life-time of 3 nsec, at 77 K.     

The temperature-composition phase diagram and the miscibility gap of Hg1-xCdxTe solid solutions by dynamic mass-loss measurements

The dynamic mass-loss technique has been employed to measure Hg partial pressures over Te-saturated Hg_1-xCd_xTe solid solutions with x = 0.40, 0.54, and 0.70 in the 10^-1 to 10^-4 atm range. The relative chemical potentials of HgTe in Hg_1-xCd_xTe solid solutions have been calculated using the measured Hg partial pressures at temperatures below 413°C, and fitted into an analytical expression. A Gibbs-Duhem integration yielded the relative chemical potentials of CdTe. By combining the relative chemical potentials of the binary components HgTe and CdTe, an expression for the Gibbs free energy of mixing was derived. The binodal (miscibility gap) and spinodal curves of the Hg_1-xCd_xTe solid solutions have been established with the critical temperature and composition of 221°C and Hg_0.40Cd_0.60Te.     

Optically pumped LPE-grown Hg1−xCdxTe lasers

Liquid phase epitaxially-grown HgCdTe crystals, which were cooled to approximately 12 K and optically pumped with a Nd:YAG laser were found to lase continuously at 2.79 Μm. In addition, pulsed laser emission in several HgCdTe crystals was observed at 77 K in the wavelength range from 1. 25 to 2. 97 Μm using a O-switched Nd:YAG laser. This work was sponsored by the Department of the Air Force.     

碲镉汞红外探测器性能调控技术研究

对影响Hg_1-xCd_xTe红外探测器性能的不同调控技术——包括材料调控(组分及温度、掺杂浓度、压强及应力等对材料性能的调控)、器件结构调控(n-on-p、p-on-n、p-i-n、n-B-n等器件结构的调控)和工艺调控(各种工艺调控对材料制备和器件制备等的影响)等——进行了简单介绍,以合理调控器件性能、有效降低器件暗电流、提高器件工作温度等,从而促进Hg_1-xCd_xTe红外探测器在降低成本、减小功耗、提高可靠性等方面的发展。     

Oxidation of Hg1−xCdxTe studied with surface sensitive techniques

We report the use of surface sensitive electron spectroscopies to monitor the initial steps of formation of a native oxide on atomically clean cleaved Hg_l-xCd_xTe single crystal surfaces in ultrahigh vacuum (UHV). Here the oxide is formed by oxygen excited by the presence of an operating ion gauge. During the reaction, the composition of the surface region of the substrate was found to change, with a net loss of Hg from the surface. Parallel studies of the compositions of thick anodic oxides using sputter profiling techniques showed only small amounts of Hg in the anodic oxides. On leave from Odense University, Denmark.     

Slider LPE of Hg1-xCdxTe using mercury pressure controlled growth solutions

Homogeneous, nearly perfect single crystals of Hg_1-xCd_xTe are extremely difficult to prepare due primarily to the high vapor pressure of mercury. However, epitaxially grown Hg_1-xCd_xTe layers have a high potential for yielding material of a substantially higher quality. Using a new, open-tube, horizontal slider-type liquid phase epitaxial (LPE) growth technique, in which mercury pressure controlled growth solutions are used, a high degree of growth solution compositional control has been demonstrated. LPE layers of Hg_1-xCd_xTe have been grown on CdTe substrates and their high quality has been confirmed by optical, transport and electron microprobe measurements. Layer thicknesses are uniform and have been varied from 5 to 40 μ by changing the degree of supercooling or the growth time. An electron carrier concentration as low as 8.6 × 10¹⁵/cm³ and electron Hall mobilities up to 2.8 × 105 cm²/V-sec at 77K have been measured on in situ annealed samples. This work was sponsored by the Department of the Air Force and the U.S. Army Research Office.     

碲镉汞量子点的离子交换能带调控及其近红外自吸收性质

通过软化学方法制备单分散的CdTe量子点,调节Hg²⁺的浓度离子交换实现从可见到近红外光谱准连续可调的碲镉汞(Hg_xCd_1-xTe)量子点制备。深入分析了近红外Hg_0.33Cd_0.67Te量子点的变温光致发光及其自吸收特性,研究结果表明：碲镉汞量子点的荧光强度随着温度的升高（0～100℃）呈线性降低趋势,谱线展宽,峰位发生红移（12nm）;量子点的吸收和发射光谱部分重叠导致自吸收效应随着量子点的浓度增加而增强,导致量子点荧光强度的降低。