Shashidhar Shintri

Rensselaer Polytechnic Institute, Troy, New York, United States

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Publications (5)3.27 Total impact

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    ABSTRACT: Low-defect density epitaxial CdTe on Si is very crucial for fabricating high performance HgCdTe IR focal planar arrays on Si. This paper discusses a novel nanopatterning technique to explore defect reduction in CdTe epitaxy on (211)Si. Nanopatterning of full 3″ (211)Si wafers was done by growing a thin layer of thermal SiO2 and patterning by molecular transfer lithography (MxL) based on water-soluble templates. Conditions for obtaining selective Ge and CdTe were obtained in the temperature range of 575-675 °C and 505-520 °C respectively. X-ray analysis of thin CdTe films grown on these substrates gave wider full-width half-maximum (FWHM) values when compared to the layers grown on blanket (non-patterned) (211)Si, which is attributed to some patterning defects and spurious nucleation on oxide side walls. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 08/2012; 9(8-9):1716-1719.
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    ABSTRACT: Metalorganic vapor phase epitaxy (MOVPE) of (211)B CdTe on (211)Si using intermediate Ge and ZnTe layers has been achieved for use as substrates for the growth of HgCdTe infrared detector materials. The best (211)B CdTe films grown in this study display a low X-ray diffraction (XRD) rocking-curve full-width-at-half-maximum (FWHM) of 64 arcs for a 12 µm thick layer and Everson etch pit density (EPD) of 3x105cm-2. In order to reduce the threading dislocation density further, growth on patterned layer has been investigated using Si3N4 as the mask. In order to achieve selective nucleation on patterned layer, process parameters were first developed. A circular pattern was used to study the anisotropy during growth and to identify the optimum orientation for parallel stripe growth windows. The optimum growth window was then used for the growth of completely merged layers (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 08/2012; 9(8-9):1712-1715.
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    ABSTRACT: We report an investigation of epitaxial germanium grown by chemical vapor deposition (CVD) on arsenic-terminated (211)Si, which is the preferred substrate in the USA for fabrication of night-vision devices based on mercury cadmium telluride (MCT) grown by molecular-beam epitaxy (MBE). The films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), cross-sectional transmission electron microscopy (XTEM), and x-ray diffraction (XRD). Arsenic passivation was found to be effective in preventing cross-contamination of unwanted residual species present inside the reactor chamber and also in prolonging the evolution of layer-by-layer growth of Ge for significantly more monolayers than on nonpassivated Si. The two-dimensional (2D) to three-dimensional (3D) transition resulted in Ge islands, the density and morphology of which showed a clear distinction between passivated and nonpassivated (211)Si. Finally, thick Ge layers (∼250nm) were grown at 525°C and 675°C with and without As passivation, where the layers grown with As passivation resulted in higher crystal quality and smooth surface morphology. KeywordsGermanium–epitaxy–chemical vapor deposition (CVD)–arsenic passivation–(211)Si
    Journal of Electronic Materials 01/2011; 40(8):1637-1641. · 1.64 Impact Factor
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    ABSTRACT: High performance HgCdTe IR detector fabrication on silicon substrates first requires low defect density CdTe buffer layers to be grown on silicon. The objective of this paper is to demonstrate dislocation reduction in CdTe epitaxial layers grown on silicon substrate by using intermediate nanocrystalline CdTe buffer layers. Colloidal synthesis of high quality CdTe nanocrystals was accomplished and spin coating of these CdTe nanocrystals as buffer layers on silicon substrates was carried out. CdTe layers were grown on these buffered substrates by metalorganic chemical vapor deposition (MOCVD). However, the incomplete removal of SiO2 on silicon substrate (by chemical treatment) prevented the exact orientation of the nanocrystals with the silicon substrate and over layer growth of continuous single crystal CdTe epitaxial film. Two new approaches were further investigated: (i) First a thin film of Ge was grown on Si, followed by the deposition of thin SiO2 followed by nanopatterning using block co-polymer (BCP) lithography. Transmission electron microscopy (TEM) showed defect reduction in the CdTe layers grown on these substrates, but the x-ray rocking curves over a larger area gave wider full width half maximum values compared to that of layers grown on blanket surfaces. This was attributed to non uniform nanopatterning in these initial studies; (ii) SiO2 coated silicon substrates were nanopatterned using interference lithography with a honeycomb array of holes. These substrates will be used for the selective growth of germanium and CdTe by MOCVD.
    Proc SPIE 08/2010;
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    ABSTRACT: We report on the investigation of epitaxial cadmium telluride grown by metalorganic vapor-phase epitaxy (MOVPE) on (211)Si, with particular emphasis on studying the effect of changing the reactor parameters and thermal annealing conditions on the epilayer quality. The CdTe films were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and x-ray diffraction (XRD). The best CdTe films were observed when the Te/Cd precursor partial pressure ratio was close to 3.1. It was also observed that, though annealing improved the crystal quality, a slight increase in surface roughness was observed. Similar attempts were made to improve the growth conditions of ZnTe intermediate buffer layer, which showed similar trends with changes in precursor flows.
    Journal of Electronic Materials 41(10). · 1.64 Impact Factor

Publication Stats

1 Citation
3.27 Total Impact Points

Institutions

  • 2011–2012
    • Rensselaer Polytechnic Institute
      • Department of Materials Science and Engineering
      Troy, New York, United States