Browsing by Author "Luc, Q. H."

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Control of metamorphic buffer structure and device performance of InxGa1-xAs epitaxial layers fabricated by metal organic chemical vapor deposition
(2014-12-05)
Nguyen, H. Q.
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Yu, H. W.
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Luc, Q. H.
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Tang, Y. Z.
;
Phan, V. T. H.
Using a step-graded (SG) buffer structure via metal-organic chemical vapor deposition, we demonstrate a high suitability of In0.5Ga0.5As epitaxial layers on a GaAs substrate for electronic device application. Taking advantage of the technique\'s precise control, we were able to increase the number of SG layers to achieve a fairly low dislocation density (similar to 10(6)cm(-2)), while keeping each individual SG layer slightly exceeding the critical thickness (similar to 80 nm) for strain relaxation. This met the demanded but contradictory requirements, and even offered excellent scalability by lowering the whole buffer structure down to 2.3 mu m. This scalability overwhelmingly excels the forefront studies. The effects of the SG misfit strain on the crystal quality and surface morphology of In0.5Ga0.5As epitaxial layers were carefully investigated, and were correlated to threading dislocation (TD) blocking mechanisms. From microstructural analyses, TDs can be blocked effectively through self-annihilation reactions, or hindered randomly by misfit dislocation mechanisms. Growth conditions for avoiding phase separation were also explored and identified. The buffer-improved, high-quality In0.5Ga0.5As epitaxial layers enabled a high-performance, metal-oxide-semiconductor capacitor on a GaAs substrate. The devices displayed remarkable capacitance-voltage responses with small frequency dispersion. A promising interface trap density of 3 x 10(12) eV(-1) cm(-2) in a conductance test was also obtained. These electrical performances are competitive to those using lattice-coherent but pricey InGaAs/InP systems.
First Experimental Demonstration of Negative Capacitance InGaAs MOSFETs With Hf0.5Zr0.5O2 Ferroelectric Gate Stack
(2018-01-01)
Luc, Q. H.
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Fan-Chiang, C. C.
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Huynh, S. H.
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Huang, P.
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Do, H. B.
We demonstrate, for the first time, the negative capacitance (NC) In0.53Ga0.47As nMOSFET with 8-nm Hf0.5Zr0.5O2 (HZO) as ferroelectric (FE) dielectric for sub-60 mV/dec subthreshold swing (SS). The impact of annealing treatments on the FE properties and electrical characteristics of NC InGaAs nMOSFETs are investigated. Optimized annealing condition results in NC effects at the HZO/Al2O3/InGaAs nMOSFETs with steep SS property (similar to 11 mV/dec).