Browsing by Author "Zhu, Y."

Now showing 1 - 4 of 4
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    Energy band alignment of atomic layer deposited HfO2 on epitaxial (110)Ge grown by molecular beam epitaxy
    Hudait, Mantu K.; Zhu, Y.; Maurya, Deepam; Priya, Shashank (AIP Publishing, 2013-03-01)
    The band alignment properties of atomic layer HfO2 film deposited on epitaxial (110)Ge, grown by molecular beam epitaxy, was investigated using x-ray photoelectron spectroscopy. The cross-sectional transmission electron microscopy exhibited a sharp interface between the (110)Ge epilayer and the HfO2 film. The measured valence band offset value of HfO2 relative to (110)Ge was 2.28 +/- 0.05 eV. The extracted conduction band offset value was 2.66 +/- 0.1 eV using the bandgaps of HfO2 of 5.61 eV and Ge bandgap of 0.67 eV. These band offset parameters and the interface chemical properties of HfO2/(110)Ge system are of tremendous importance for the design of future high hole mobility and low-power Ge-based metal-oxide transistor devices. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794838]
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    Quantitative phase spectroscopy
    Rinehart, M.; Zhu, Y.; Wax, A. (2012-05-01)
    Quantitative phase spectroscopy is presented as a novel method of measuring the wavelength-dependent refractive index of microscopic volumes. Light from a broadband source is filtered to an ~5 nm bandwidth and rapidly tuned across the visible spectrum in 1 nm increments by an acousto-optic tunable filter (AOTF). Quantitative phase images of semitransparent samples are recovered at each wavelength using off-axis interferometry and are processed to recover relative and absolute dispersion measurements. We demonstrate the utility of this approach by (i) spectrally averaging phase images to reduce coherent noise, (ii) measuring absorptive and dispersive features in microspheres, and (iii) quantifying bulk hemoglobin concentrations by absolute refractive index measurements. Considerations of using low coherence illumination and the extension of spectral techniques in quantitative phase measurements are discussed.
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    Structural properties and band offset determination of p-channel mixed As/Sb type-II staggered gap tunnel field-effect transistor structure
    Zhu, Y.; Jain, N.; Mohata, Dheeraj K.; Datta, Suman; Lubyshev, Dmitri; Fastenau, Joel M.; Liu, A. K.; Hudait, Mantu K. (AIP Publishing, 2012-09-01)
    The structural properties and band offset determination of p-channel staggered gap In0.7Ga0.3As/GaAs0.35Sb0.65 heterostructure tunnel field-effect transistor (TFET) grown by molecular beam epitaxy (MBE) were investigated. High resolution x-ray diffraction revealed that the active layers are strained with respect to "virtual substrate." Dynamic secondary ion mass spectrometry confirmed an abrupt junction profile at the In0.7Ga0.3As/GaAs0.35Sb0.65 heterointerface and minimal level of intermixing between As and Sb atoms. The valence band offset of 0.37 +/- 0.05 eV was extracted from x-ray photoelectron spectroscopy. A staggered band lineup was confirmed at the heterointerface with an effective tunneling barrier height of 0.13 eV. Thus, MBE-grown staggered gap In0.7Ga0.3As/GaAs0.35Sb0.65 TFET structures are a promising p-channel option to provide critical guidance for the future design of mixed As/Sb type-II based complementary logic and low power devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752115]
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    Ultra-high frequency photoconductivity decay in GaAs/Ge/GaAs double heterostructure grown by molecular beam epitaxy
    Hudait, Mantu K.; Zhu, Y.; Johnston, Steve W.; Maurya, Deepam; Priya, Shashank; Umbel, Rachel (AIP Publishing, 2013-03-01)
    GaAs/Ge/GaAs double heterostructures (DHs) were grown in-situ using two separate molecular beam epitaxy chambers. High-resolution x-ray rocking curve demonstrates a high-quality GaAs/Ge/GaAs heterostructure by observing Pendellosung oscillations. The kinetics of the carrier recombination in Ge/GaAs DHs were investigated using photoconductivity decay measurements by the incidence excitation from the front and back side of 15 nm GaAs/100 nm Ge/0.5 mu m GaAs/(100) GaAs substrate structure. High-minority carrier lifetimes of 1.06-1.17 mu s were measured when excited from the front or from the back of the Ge epitaxial layer, suggests equivalent interface quality of GaAs/Ge and Ge/GaAs. Wavelength-dependent minority carrier recombination properties are explained by the wavelength-dependent absorption coefficient of Ge. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794984]