资料简介索引

红外技术 6001 Hg_(1-x)Cd_xTe的缺陷化学和鉴定 Defect chemistry aad characterization of Hg_(1-x) Cd_xTe,H.R.Vydyanath,N.81.23 924,105p(1981). 碲镉汞晶体未掺杂,置于400～655℃和不同汞压下进行平衡。对淬火到室温随后作高温平衡的晶体作霍尔放应和迁移率测量。根据此种样品在77K下空穴浓度随Hg分压的变化以及与掺铟和磷样品的比较,得出未掺杂晶体的缺陷模型。根据模型阐述了晶体缺陷和p-n转型的性质。     

Hg_(1-x)Cd_xTe上的阳极硫化物薄膜

本文描述在Hg_(1-x)Cd_xTe上形成自身硫化物薄膜的一种新的阳极硫化法。这种新方法是利用自身硫化物薄膜而不是自身氧化物薄膜连接晶格和钝化表面。俄歇电子光谱学分析的结果表明,自身形成的均匀CdS薄膜具有突变的界面转换。金属—绝缘体—半导体器件的电容—电压特性的测量表明,薄膜具有低和负的固定表面电荷密度,约为-1×10~(11)电子·厘米~(-2),还有较低浓度的快表面电荷密度。自身硫化物薄膜使p型Hg_(1-x)Cd_xTe表面差不多处于平带,这一点优于使p型材料表面反型的自身氧化物薄膜。这种新的表面钝化法特别适用于用p型Hg_(1-x)Cd_xTe制备的光伏二极管。     

碲镉汞晶体补偿度的研究

对于8～14微米Hg_(1-x)Cd_xTe晶体材料,已测量了4.2～300 K温度范围内的霍尔系数和电阻率,获得了载流子浓度和迁移率随温度变化的关系。在载流子浓度非完全简并的条件下,根据杂质饱和电离散射所确定的迁移率,计算了三个样品的补偿度。并且通过电中性方程验算了迁移率法计算补偿度的准确性。     

利用Hg压控制生长溶液的Hg_(1-x)Cd_xTe滑移接触液相外延

制备均匀的接近完整的Hg_(1-x)Cd_xTe单晶非常困难,其主要原因是Hg的蒸汽压高。然而,用外延生长Hg_(1-x)Cd_xTe薄层得到基本上质量较高的材料却具有很大的潜力。采用一种新的、开管、水平滑移接触型液相外延(LPE)生长工艺,在这种工艺中,利用Hg压控制生长溶液,并证明了生长溶液的组份得到了高度的控制。在CdTe衬底上生长了Hg_(1-x)Cd_xTe的液相外延层,用光学输运测量和电子显微镜探针测量,进一步证实了外延层的高质量。薄层厚度均匀,通过改变过冷度或生长时间,层厚在5到40微米间变化。在原生长位置上退火的样品,77K下测量的结果是:电子载流子浓度低至8.6×10~(15)/厘米~3,电子的霍尔迁移率可达到2.8×10~5厘米/伏·秒。     

汞退火对分子束外延生长的HgCdTe电学特性的影响

在测量霍尔效应时,用分子束外延(MBE)生长的Hg_(1-x)Cd_xTe膜层常表现出异常的电导特性,通过在汞气氛中退火,能明显消除这种现象,并转变为均匀的p型导体。用霍尔效应测量表征的膜层来研究退火对它的影响。本文给出了退火后p型膜层中迁移率与Cd组份x值和受主能级的关系。     

Hg_(1-x)Cd_xTe的分子束外延生长及特性

在用分子束外延法(MBE)生长Hg_(1-x)Cd_xTe合金系时要特别重视这种材料的下述特性:(1) 在150℃以上,组分值x为0.2～0.3的Hg_(1-x)Cd_xTe会很快分解并变得非常不一致;(2) 汞的粘附系数很低,小于0.03;(3) 汞蒸汽压很高。由于Hg_(1-x)Cd_xTe合金系的分解速度随温度降低而快速下     

Hg_(1-x)Cd_xTe平面型In扩散及Hg扩散PN结的交流特性

Hg_(1-x)Cd_xTe材料是一种缺陷半导体,它既可通过控制缺陷成结,也可用掺杂方法成结。掺杂的方法又有扩散及离子注入两种。对不同形式的Hg_(1-x)Cd_xTe PN结的性能进行研究,将有助于对Hg_(1-x)Cd_xTe PN结的物理过程的理解。另一方面,平面工艺又是研制红外焦平     

窄禁带半导体的自由载流子吸收

从理论和实验上研究了77K和300K温度下,本征型半导体InSb,Hg_(1-x)Cd_xTe,Hg_(1-x)Mn_xTe和高掺杂Hg_(1-x)Cd_xTe在2.5～50μm波段范围内的自由载流子吸收,结果表明:对于所研究的三种本征型样品,均是极性光学声子散射起主要作用,对于InSb还应考虑声学声子和电离杂质散射。对有缺陷的Hg_(1-x)Mn_xTe样品,理论计算的自由载流子吸收系数与实验值不一致,表明存在附加的散射机制,对高掺杂Hg_(1-x)Cd_xTe的研究证实了这一假设。还讨论了非弹性电子-声子散射机制的起因,估算了特性参数。     

用常规的滑块舟液相外延生长Hg_(1-x)Cd_xTe和退火对外延层特性的影响

在开管流动氢气的常规滑块舟系统中,在CdTe(111)A面衬底上已液相外延出Hg_(1-x)Cd_xTe(0.17≤x≤0.3)外延层。对于x=0.2的原生层,空穴浓度为10~(17)～10~(18)cm~(-3),霍尔迁移率为100～500cm~2/Vs,层的表面类似于镜面,外延层的电子微探针分析(EMPA)数据表明,外延层和衬底间的界面有陡的组分过渡,在汞压下,研究了250℃～400℃的温度范围内退火对原生层特性的影响。在400℃退火时,在接近界面处观察到组分变化。与此相反,在250℃～300℃的温度范围内退火时得到性能好的n型层,没有明显的组分变化。且在CdTe衬底的(111)A面上连续生长成双异质结Hg_(1-x)Cd_xTe/Hg_(1-y)Cd_yTe。     

红外超优质HgCdTe等温生长改进法

用等温生长法在CdTe衬底上生长的Hg_(1-x)Cd_xTe外延层具有镜面状表面形态、径向组分均匀度高和突出的电子特性(即x接近0.15的电子迁移率数值为500000厘米~2/伏-秒)。生长法的新特点是利用富碲HgCdTe而不是以前采用的HgTe(或化学计量Hg_(1-x)Cd_xTe)作源材料。改变源材料组分和生长温度就可得到所要求的x值。利用热管来达到高精度控温以及使液体(源)和气相中的对流减到最小。     

Hg1—xCdxTe材料中的Te离子空位共振能级

利用拉曼显微镜在室温下对金属有机化合物气相外延（MOVPE）和液相外延（LPE）方法生长的Hg1-xCdxTe薄膜材料以及用加速坩埚旋转布里奇曼（ACRT－Bridgman)和Te溶剂方法生长的Hg1-xCdxTe体材料进行了系统研究，在上述4种方法生长的材料的显微拉曼光谱中，均发现在导带底上方且远高于材料导带底对应能级的显微荧光发光峰，通过详细比较可以判定，高于导带底约1．5eV的显微荧光起源于Hg1-xCdxTe材料中的Te离子空位与材料导带底的共振能级发光，从而确定在碲镉汞材料中存在一个稳定的Te离子空位共振能级。     

A study of galvanomagnetic phenomena in MBE-grown n-CdxHg1−x Te films

The magnetic-field dependences of the Hall coefficient and the conductivity of n-type Cd_xHg_1?x Te epitaxial structures were measured at 77 K. The structures were grown by molecular-beam epitaxy with a prescribed solid solution composition profile across the thickness. A specific feature of the obtained dependences is that the conductivity and the absolute value of the Hall coefficient decrease with an increasing magnetic field. The obtained experimental dependences can only be described in terms of a model including low-mobility electrons. It is shown that anodic oxide deposited onto the Cd_xHg_1?x Te film surface makes the concentration of low-mobility electrons higher and that of anodic fluoride lower. The possible reasons for the appearance of low-mobility electrons are discussed. The most probable sources of such electrons are surface layers and electrical microheterogeneities in Cd_xHg_1?x Te films.     

CdZnTe衬底对碲镉汞气相外延表面形貌的影响

利用气相外延技术在CdZnTe衬底上生长Hg1-xCdxTe薄膜材料,通过在不同晶向、不同极性、不同晶向偏离角度CdZnTe衬底上的外延结果发现,CdZnTe衬底对外延形貌的影响非常大。(111)面衬底上外延形貌明显优于(211)面衬底的外延形貌。对于同是<111>CdZnTe晶向的衬底,(111)Cd面CdZnTe衬底上的外延形貌明显优于(111)Te面。对于(111)Cd面CdZnTe衬底,当晶向偏离角度不同时,其外延形貌也有差异,晶向偏离角越小表面形貌越好。     

Examination of properties of epitaxial and bulk gallium antimonide

Using the Hall method, regularities of Te doping of GaSb grown by the Czochralski method and by liquid-phase epitaxy (LPE) are studied. Optimum epitaxial conditions that enable the growth of Te-doped GaSb layers with higher carrier mobilities than the bulk Czochralski-grown GaSb are determined. Possibilities of improvement of output parameters of photoconverters obtained by diffusion of Zn into n-GaSb from the gas phase and by LPE are discussed.     

Annealing experiments in heavily arsenic-doped (Hg,Cd)Te

Arsenic doped molecular beam epitaxy (MBE) (Hg,Cd)Te films were grown on (Cd,Zn)Te substrates. The concentration of arsenic was varied from 5 x 10¹⁸ cm^-3 to 1 x 10²⁰ cm^-3. After the growth, the epitaxial layers were annealed at various partial pressures of Hg within the existence region of (Hg,Cd)Te at temperatures ranging from 400 to 500°C. Hall effect and resistivity measurements were carried out subsequent to the anneals. 77K hole concentration measurements indicate that for concentrations of arsenic <10¹⁹ cm⁻³, most of the arsenic is electrically active acting as acceptors interstitially and/or occupying Te lattice sites at the highest Hg pressures. At lower Hg pressures, particularly at annealing temperatures of 450°C and higher, compensation by arsenic centers acting as donors appears to set in and the hole concentration decreases with decrease in Hg pressure. These results indicate the amphoteric behavior of arsenic and its similarity to the behavior of phosphorus in (Hg,Cd)Te previously inferred by us. A qualitative model which requires the presence of arsenic occupying both interstitial and Te lattice sites along with formation of pairs of arsenic centers is conjectured.     

Te vapor pressure dependence of the pn junction properties of PbTe liquid phase epitaxial layers

The pn junction characteristics of the PbTe epitaxial layers grown on PbTe substrates are investigated. Both the substrate crystals and the epitaxial layers are grown under controll Te vapor pressures. The ideality factors n of pn junctions decrease close to 1 in the temperature region from 40K to about 120K, but then increase with increasing temperature. The increase of n is more pronounced for higher Te vapor pressure. As a possible origin of the recombination current, deep levels with E_d=0.09 eV are found from Hall measurements for pn junctions grown under higher Te vapor pressure.     

Lpe growth of Hgl−xCdxTe using conventional slider boat and effects of annealing on properties of the epilayers

The epitaxial layers of Hg_1−xCd_xTe (0.17≦×≦0.3) were grown by liquid phase epitaxy on CdTe (111)A substrates using a conventional slider boat in the open tube H₂ flow system. The as-grown layers have hole concentrations in the 10¹⁷− 10¹⁸ cm⁻³ range and Hall mobilities in the 100−500 cm²/Vs range for the x=0.2 layers. The surfaces of the layers are mirror-like and EMPA data of the layers show sharp compositional transition at the interface between the epitaxial layer and the substrate. The effects of annealing in Hg over-pressure on the properties of the as-grown layers were also investigated in the temperature range of 250−400 °C. By annealing at the temperature of 400 °C, a compositional change near the interface is observed. Contrary to this, without apparent compositional change, well-behaved n-type layers are obtained by annealing in the 250−300 °C temperature range. Sequential growth of double heterostructure, Hg_l−xCd_xTe/Hg_l−yCd_yTe on a CdTe (111)A substrate was also demonstrated.     

X-ray Diffraction Imaging of Improved Bulk-Grown CdZnTe(211) and Its Comparison with Epitaxially Grown CdTe Buffer Layers on Si and Ge Substrates

Large-area high-quality Hg_1–x Cd _x Te sensing layers for infrared imaging in the 8 μm to 12 μm spectral region are typically grown on bulk Cd_1–x Zn _x Te substrates. Alternatively, epitaxial CdTe grown on Si or Ge has been used as a buffer layer for high-quality epitaxial HgCdTe growth. In this paper, x-ray topographs and rocking-curve full-width at half-maximum (FWHM) data will be presented for recent high-quality bulk CdZnTe grown by the vertical gradient freeze (VGF) method, previous bulk CdZnTe grown by the vertical Bridgman technique, epitaxial CdTe buffer layers on Si and Ge, and a HgCdTe layer epitaxially grown on bulk VGF CdZnTe.     

Thermomigration of Te precipitates and improvement of (Cd,Zn)Te substrate characteristics for the fabrication of LWIR (Hg,Cd)Te photodiodes

(Cd,Zn)Te wafers containing Te precipitates have been annealed under well defined thermodynamic conditions at temperatures below and above the melting of Te. Results of the examination of the wafers with infrared microscopy before and after the anneals indicate a substantial reduction of the Te precipitates in wafers annealed at temperatures in excess of the melting point of Te compared with those annealed at temperatures below the melting point of Te. These results confirm the thermomigration of liquid Te precipitates to be the principally operative mechanism during annealing in the elimination of these precipitates in (Cd,Zn)Te wafers. The occurrence of Te precipitates in (Hg,Cd)Te epitaxial layers grown on (Cd,Zn)Te substrates containing Te precipitates is also explained on the basis of thermomigration of these precipitates during LPE growth from the substrates to the epilayers. Absence of occurrence of Te precipitates in (Hg,Cd)Te epilayers grown on annealed (Cd,Zn)Te substrates with negligible Te precipitates is also confirmed. Usefulness of annealing (Cd,Zn)Te substrates—to eliminate Te precipitates—prior to epilayer growth is confirmed via demonstration of improved long wavelength infrared (Hg,Cd)Te device array performance uniformity in epitaxial layers grown on (Cd,Zn)Te substrates with negligible Te precipitates after annealing.     

The growth and characterization of (211) and (133) Oriented (Hg,Cd)Te epilayers (211)B GaAs by organometallic vapor phase epitaxy

The growth of CdTe buffer layers on (211)B GaAs substrates by organometallic vapor phase epitaxy (OMVPE) was studied, and it was found that, depending on the growth conditions, either the (211) or (133) epitaxial orientation could be formed. In some cases, an epilayer showing a mixed (211) and (133) orientation was also observed. The influence of several growth parameters on the orientation of the CdTe layer was investigated, and it was found that the Te/Cd ratio, together with the growth temperature, have the most significant effect in determining the epilayer orientation. From these results, it was then possible to select nominally optimized growth conditions for CdTe buffer layers of both orientations. (Hg,Cd)Te layers of the same orientations could then be grown and characterized. Although double crystal x-ray diffraction measurements indicated a somewhat better crystalline perfection in the (133) (Hg,Cd)Te layers, these layers showed a poor surface morphology compared to the (211) orientation. Measurement of etch pit densities also indicated defect densities to be typically half an order of magnitude higher in the (133) orientation. Diodes were formed by ion implantation in both orientations and significantly better results were obtained on the (211) (Hg,Cd)Te layers.