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41.
X-ray diffraction full-width at half-maximum (XRD FWHM), reflection high-energy electron diffraction (RHEED), and atomic force microscopy (AFM) indicate a mosaic structure for molecular-beam epitaxy (MBE) (211)B CdTe/Si. AFM measurements indicate long, thin, small-angle-disoriented grains for CdTe/Si epilayers. These disoriented grains are ~1 μm in the [] direction and are ~40 nm in the [] direction. The RHEED pattern in the [] direction depicts nearly ideal single-crystal periodicity. The RHEED pattern in the [] direction is indicative of small-angle-disoriented crystalline grains. Scanning electron microscopy (SEM), AFM, and XRD measurements all indicate an approximate factor of 10 increase in the Everson etch pit density (EPD) over standard Nomarski microscopy Everson EPD determination.  相似文献   
42.
The possibility to prepare semi-insulating CdTe with a deep-level doping below the limit 1013 cm−3 demanded in detector industry is studied theoretically within quasi-chemical formalism. We show that proper thermal treatment, including low temperature (ca 200°C) dwell, allows fulfillment of this demand also in 7N or less purity materials. The procedure is demonstrated in Te-rich CdTe doped with a shallow donor. Its principle is based on enhanced defect selfcompensation, which affords at sufficiently low temperature extremely high compensation of shallow defects. New high-temperature transport data are used to refine on previous native defect properties for the modeling. The analysis of diffusion rates at lowered temperature approves the model for a real-time experimental verification.  相似文献   
43.
The cost and performance of hybrid HgCdTe infrared (IR) focal plane arrays are constrained by the necessity of fabricating the detector arrays on a CdZnTe substrate. These substrates are expensive, fragile, available only in small rectangular formats, and are not a good thermal expansion match to the silicon readout integrated circuit. We discuss in this paper an IR sensor technology based on monolithically integrated IR focal plane arrays that could replace the conventional hybrid focal plane array technology. We have investigated the critical issues related to the growth of HgCdTe on Si read-out integrated circuits and the fabrication of monolithic focal plane arrays: (1) the design of Si read-out integrated circuits and focal plane array layouts; (2) the low-temperature cleaning of Si(001) wafers; (3) the growth of CdTe and HgCdTe layers on read-out integrated circuits; (4) diode creation, delineation, electrical, and interconnection; and (4) demonstration of high yield photovoltaic operation without limitation from earlier preprocessing such as substrate cleaning, molecular beam epitaxy (MBE) growth, and device fabrication. Crystallographic, optical, and electrical properties of the grown layers will be presented. Electrical properties for diodes fabricated on misoriented Si and readout integrated circuit (ROIC) substrates will be discussed. The fabrication of arrays with demonstrated I–V properties show that monolithic integration of HgCdTe-based IR focal plane arrays on Si read-out integrated circuits is feasible and could be implemented in the third generation of IR systems.  相似文献   
44.
Nano imprinting technology and the electrodeposition method were applied to make CdTe nano patterns on flexible substrates. An ammonia based aqueous solution was prepared at pH 10.7 and indium tin oxide (ITO)/polyethylene naphthalate (PEN) film with template was used as the working electrode. ITO thin film which was coated on PEN film had good electrical conductivity and optical transmittance. The template was manufactured by nano imprinting technology on ITO/PEN film. It was made from benzyl methacrylate and had nano rod arrays. It was used as the working electrode and for making CdTe nano pattern. CdTe nano pattern were analyzed by X-ray diffractometer, dual beam (DB)-focused ion beam (FIB)-scanning electron microscopy (SEM), Raman spectroscopy, and ultraviolet (UV)-visible (VIS) spectroscopy. The structure and optical properties of CdTe nano pattern on flexible substrates was analyzed. The crystalline size of nano pattern had 8.26 nm. The Te particles that were precipitated on CdTe surface seems to be exist. The absence of annealing process influenced to have low absorption coefficient and narrow band gap compared to bulk CdTe. However, nano pattern increased reflectance.  相似文献   
45.
Sn-doped CdTe polycrystalline films were successfully deposited on ITO glass substrates by close space sublimation. The effects of Sn-doping on the microstructure, surface morphology, and optical properties of polycrystalline films were studied using X-ray diffraction, scanning electron microscopy, and ultraviolet-visible spectrophotometry, respectively. The results show that the lower molar ratio of Sn and CdTe conduces to a strongly preferential orientation of (111) in films and a larger grain size, which indicates that the crystallinity of films can be improved by appropriate Sn-doping. As the molar ratio of Sn and CdTe increases, the preferential orientation of (111) in films becomes weaker, the grain size becomes smaller, and the crystal boundary becomes indistinct, which indicates that the crystallization growth of films is incomplete. However, as the Sn content increases, optical absorption becomes stronger in the visible region. In summary, a strongly preferential orientation of (111) in films and a larger grain size can be obtained by appropriate Sn-doping (molar ratio of Sn : CdTe = 0.06 : 1), while the film retains a relatively high optical absorption in the visible region. However, Sn-doping has no obvious influence on the energy gap of CdTe films.  相似文献   
46.
By mans of a chemical synthesis technique stoichiometric CdTe-nanocrystals thin films were prepared on glass substrates at 70 °C. First, Cd(OH)2 films were deposited on glass substrates, then these films were immersed in a growing solution prepared by dissolution of Te in hydroxymethane sulfinic acid to obtain CdTe. The structural analysis indicates that CdTe thin films have a zinc-blende structure. The average nanocrystal size was 19.4 nm and the thickness of the films 170 nm. The Raman characterization shows the presence of the longitudinal optical mode and their second order mode, which indicates a good crystalline quality. The optical transmittance was less than 5% in the visible region (400–700 nm). The compositional characterization indicates that CdTe films grew with Te excess.  相似文献   
47.
The vision of achieving a completely in-vacuum process for fabricating HgCdTe detector arrays is contingent on the availability of a vacuumcompatible photolithography technology. One such technology for vacuum photolithography involves the use of amorphous-hydrogenated Si (a-Si:H) as a photoresist. In this work, we deposit a-Si:H resists via plasma-enhanced chemical-vapor deposition (PECVD) using an Ar-diluted silane precursor. The resists are then patterned via excimer laser exposure and development etched in a hydrogen plasma where etch selectivities between unexposed and exposed regions exceed 600:1. To determine the best conditions for the technique, we investigate the effects of different exposure environments and carry out an analysis of the a-Si:H surfaces before and after development etching. Analysis via transmission electron microscopy (TEM) reveals that the excimer-exposed surfaces are polycrystalline in nature, indicating that the mechanism for pattern generation in this study is based on melting and crystallization. To demonstrate pattern transfer, underlying CdTe films were etched (after development of the resist) in an electron cyclotron resonance (ECR) plasma, where etch selectivities of approximately 8:1 have been achieved. The significance of this work is the demonstration of laser-induced poly-Si as an etching mask for vacuum-compatible photolithography.  相似文献   
48.
氩氧气氛下沉积的CdTe薄膜及太阳电池的性质   总被引:7,自引:2,他引:7  
研究了在氩氧气氛下近空间升华沉积CdTe的技术.发展了在表面十分平整的玻璃衬底上沉积优质CdTe薄膜的方法,对比了在玻璃衬底和CdS薄膜上CdTe薄膜的结构特征.通过研究氧分压对CdTe薄膜择优取向的影响,证实了在恰当的近空间升华沉积过程中,两种衬底上的CdTe薄膜具有相同的结构.研究了玻璃衬底上CdTe薄膜的电学与光学性质,观察了后处理对上述薄膜性质的影响,并研制出了效率达1338%的小面积CdTe 薄膜太阳电池.  相似文献   
49.
We report on continuing efforts to develop a reproducible process for molecular beam epitaxy of CdZnTe on three-inch, (211) Si wafers. Through a systematic study of growth parameters, we have significantly improved the crystalline quality and have reduced the density of typical surface defects. Lower substrate growth temperatures (∼250–280°C) and higher CdZnTe growth rates improved the surface morphology of the epilayers by reducing the density of triangular surface defects. Cyclic thermal annealing was found to reduce the dislocation density. Epilayers were characterized using Nomarski microscopy, scanning electron microscopy, x-ray diffraction, defect-decoration etching, and by their use as substrates for HgCdTe epitaxy.  相似文献   
50.
Polycrystalline Cadmium Telluride (CdTe) thin films were prepared on glass substrates by thermal evaporation at the chamber ambient temperature and then annealed for an hour in vacuum ~1×10−5 mbar at 400 °C. These annealed thin films were doped with copper (Cu) via ion exchange by immersing these films in Cu (NO3)2 solution (1 g/1000 ml) for 20 min. Further these films were again annealed at different temperatures for better diffusion of dopant species. The physical properties of an as doped sample and samples annealed at different temperatures after doping were determined by using energy dispersive x-ray analysis (EDX), x-ray diffraction (XRD), Raman spectroscopy, transmission spectra analysis, photoconductivity response and hot probe for conductivity type. The optical band gap of these thermally evaporated Cu doped CdTe thin films was determined from the transmission spectra and was found to be in the range 1.42–1.75 eV. The direct energy band gap was found annealing temperatures dependent. The absorption coefficient was >104 cm−1 for incident photons having energy greater than the band gap energy. Optical density was observed also dependent on postdoping annealing temperature. All samples were found having p-type conductivity. These films are strong potential candidates for photovoltaic applications like solar cells.  相似文献   
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