Browsing by Author "Liu, Chee-Wee"

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A Comprehensive Study of Ge1-xSix on Ge for the Ge nMOSFETs with Tensile Stress, Shallow Junctions and Reduced Leakage
(2009)
Luo, Guang-Li
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Huang, Shih-Chiang
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Chung, Cheng-Ting
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Heh, Dawei
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Chien, Chao-Hsin
For the first time, growth of high-quality Ge-rich Ge1-xSix (0 <= x <= 0.14) layers on Ge substrate was demonstrated. An effective suppression of the phosphorus diffusion in Ge1-xSix and a better thermal stability of the nickel germanide on Ge1-xSix were observed. A higher rectifying ratio with a reduced diode leakage current in n(+)-Ge1-xSix/p-Ge1-xSix is compared with n(+)-Ge/p-Ge. These results indicate that it is suitable for Ge1-xSix to be used as source/drain (S/D) to fabricate the uniaxial tensile-strained channel Ge nMOSFETs.
High quality Ge thin film grown by ultrahigh vacuum chemical vapor deposition on GaAs substrate
(2011-04-18)
Tang, Shih-Hsuan
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Chang, Edward Yi
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Hudait, Mantu
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Maa, Jer-Shen
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Liu, Chee-Wee
High-quality epitaxial Ge films were grown on GaAs substrates by ultrahigh vacuum chemical vapor deposition. High crystallinity and smooth surface were observed for these films by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. Direct band gap emission (1550 nm) from this structure was detected by photoluminescence. Valence band offset of 0.16 eV at the Ge/GaAs interface was measured by x-ray photoelectron spectroscopy. N-type arsenic self-doping of 10(18)/cm(-3) in the grown Ge layers was determined using electrochemical capacitance voltage measurement. This structure can be used to fabricate p-channel metal-oxide-semiconductor field-effect transistor for the integration of Ge p-channel device with GaAs n-channel electronic device. (C) 2011 American Institute of Physics. [doi:10.1063/1.3580605]
Solid Solubility Limited Dopant Activation of Group III Dopants (B, Ga & In) in Ge Targeting sub-7nm Node Low p plus Contact Resistance
(2017-01-01)
Borland, John
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Lee, Yao-Jen
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Chuang, Shang-Shiun
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Tseng, Tseung-Yuen
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Liu, Chee-Wee
Suppression of surface recombination in CuInSe2 (CIS) thin films via Trioctylphosphine Sulfide (TOP:S) surface passivation
(2016-03)
Luo, Shi
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Eisler, Carissa
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Wong, Tsun-Hsin
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Xiao, Hai
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Lin, Chuan-En
CuInSe2 (CIS) solar cells are promising candidates for thin film photovoltaic applications, one key limitation in their performance is surface recombination in these thin films. We demonstrate that passivating CIS films with Trioctylphosphine Sulfide (TOP:S) solution increases photoluminescence (PL) intensity by a factor of similar to 30, which suggests that this passivation significantly reduces surface recombination. X-ray photoelectron spectroscopy (XPS) reveals that TOP:S forms both -S and -P bonds on the CIS film surface, which leads to a similar to 4-fold increase in the surface Na peak intensity. This value is significantly higher than what would be expected from high temperature annealing alone, which has been linked to improvements in surface morphology and device efficiency in CIGS solar cells. We use Energy Dispersive X-ray Spectroscopy (EDS) to measure the solid-state transport of Na within CIS films with and without passivation. EDS spectra on CIS film cross-sections reveals a saddle-shaped Na profile in the as fabricated films and a concentration gradient towards the film surface in the passivated films, with 20% higher surface Na content compared with the unpassivated films. We employ Hybrid (B3PW91) Density Functional Theory (DFT) to gain insight into energetics of Na defects, which demonstrate a driving force for Na diffusion from bulk towards the surface. DFT Calculations with TOP:S-like molecules on the same surfaces reveal a similar to 1eV lower formation energy for the Na-cu defect. The experiments and computations in this work suggest that TOP:S passivation promotes Na diffusion towards CIS film surfaces and stabilizes surface Na defects, which leads to the observed substantial decrease in surface recombination. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.