Browsing by Author "Liu, Amy K."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Band offset determination of mixed As/Sb type-II staggered gap heterostructure for n-channel tunnel field effect transistor application
    Zhu, Yizheng; Jain, Nikhil; Mohata, Dheeraj K.; Datta, Suman; Lubyshev, Dmitri; Fastenau, Joel M.; Liu, Amy K.; Hudait, Mantu K. (American Institute of Physics, 2013-01-14)
    The experimental study of the valence band offset (Delta E-v) of a mixed As/Sb type-II staggered gap GaAs0.35Sb0.65/In0.7Ga0.3As heterostructure used as source/channel junction of n-channel tunnel field effect transistor (TFET) grown by molecular beam epitaxy was investigated by x-ray photoelectron spectroscopy (XPS). Cross-sectional transmission electron micrograph shows high crystalline quality at the source/channel heterointerface. XPS results demonstrate a Delta E-v of 0.39 +/- 0.05 eV at the GaAs0.35Sb0.65/In0.7Ga0.3As heterointerface. The conduction band offset was calculated to be similar to 0.49 eV using the band gap values of source and channel materials and the measured valence band offset. An effective tunneling barrier height of 0.21 eV was extracted, suggesting a great promise for designing a metamorphic mixed As/Sb type-II staggered gap TFET device structure for low-power logic applications. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775606]
  • Thumbnail Image
    Defect assistant band alignment transition from staggered to broken gap in mixed As/Sb tunnel field effect transistor heterostructure
    Zhu, Yizheng; Jain, Nikhil; Vijayaraghavan, S.; Mohata, Dheeraj K.; Datta, Suman; Lubyshev, Dmitri; Fastenau, Joel M.; Liu, Amy K.; Monsegue, Niven; Hudait, Mantu K. (American Institute of Physics, 2012-11-01)
    The compositional dependence of effective tunneling barrier height (E-beff) and defect assisted band alignment transition from staggered gap to broken gap in GaAsSb/InGaAs n-channel tunnel field effect transistor (TFET) structures were demonstrated by x-ray photoelectron spectroscopy (XPS). High-resolution x-ray diffraction measurements revealed that the active layers are internally lattice matched. The evolution of defect properties was evaluated using cross-sectional transmission electron microscopy. The defect density at the source/channel heterointerface was controlled by changing the interface properties during growth. By increasing indium (In) and antimony (Sb) alloy compositions from 65% to 70% in InxGa1-xAs and 60% to 65% in GaAs1-ySby layers, the E-beff was reduced from 0.30 eV to 0.21 eV, respectively, with the low defect density at the source/channel heterointerface. The transfer characteristics of the fabricated TFET device with an E-beff of 0.21eV show 2x improvement in ON-state current compared to the device with E-beff of 0.30 eV. On contrary, the value of E-beff was decreased from 0.21 eV to -0.03 eV due to the presence of high defect density at the GaAs0.35Sb0.65/In0.7Ga0.3As heterointerface. As a result, the band alignment was converted from staggered gap to broken gap, which leads to 4 orders of magnitude increase in OFF-state leakage current. Therefore, a high quality source/channel interface with a properly selected E-beff and well maintained low defect density is necessary to obtain both high ON-state current and low OFF-state leakage in a mixed As/Sb TFET structure for high-performance and lower-power logic applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4764880]