Browsing by Author "Wong, Y. Y."

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Effect of graded-temperature arsenic prelayer on quality of GaAs on Ge/Si substrates by metalorganic vapor phase epitaxy
(2011-10-24)
Yu, H. W.
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Chang, E. Y.
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Yamamoto, Y.
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Tillack, B.
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Wang, W. C.
The growth of GaAs epitaxy on Ge/Si substrates with an arsenic prelayer grown with graded temperature ramped from 300 to 420 degrees C is investigated. It is demonstrated that the graded-temperature arsenic prelayer grown on a Ge/Si substrate annealed at 650 degrees C not only improves the surface morphology (roughness: 1.1 nm) but also reduces the anti-phase domains' (APDs) density in GaAs epitaxy (dislocation density: similar to 2 x 10(7) cm(-2)). Moreover, the unwanted interdiffusion between Ge and GaAs epitaxy is suppressed by using the graded-temperature arsenic prelayer due to the low energy of the Ge-As bond and the use of a low V/III ratio of 20. (C) 2011 American Institute of Physics. [doi:10.1063/1.3656737]
Effect of substrate misorientation on the material properties of GaAs/Al(0.3)Ga(0.7)As tunnel diodes
(2010-12-06)
Yu, H. W.
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Chang, E. Y.
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Nguyen, H. Q.
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Chang, J. T.
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Chung, C. C.
The effect of substrate misorientation on the material quality of the N(++)-GaAs/P(++)-AlGaAs tunnel diodes (TDs) grown on these substrates is investigated. It is found that the misorientation influences both surface roughness and interface properties of the N(++)-GaAs/P(++)-AlGaAs TDs. Smooth surface (rms roughness: 1.54 angstrom) and sharp interface for the GaAs/Al(0.3)Ga(0.7)As TDs were obtained when the (100) tilted 10 degrees off toward [111] GaAs substrate was used. Besides, the oxygen content in N(++)-GaAs and P(++)-AlGaAs layers grown on the 10 degrees off GaAs substrates was reduced due to the reduction of sticking coefficient and number of anisotropic sites. (C) 2010 American Institute of Physics. [doi:10.1063/1.3525158]
Effect of substrate misorientation on the material properties of GaAs/Al0.3Ga0.7As tunnel diodes
(2010-12-06)
Yu, H. W.
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Chang, E. Y.
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Nguyen, H. Q.
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Chang, J. T.
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Chung, C. C.
The effect of substrate misorientation on the material quality of the N++-GaAs/P++-AlGaAs tunnel diodes (TDs) grown on these substrates is investigated. It is found that the misorientation influences both surface roughness and interface properties of the N++-GaAs/P++-AlGaAs TDs. Smooth surface (rms roughness: 1.54 angstrom) and sharp interface for the GaAs/Al0.3Ga0.7As TDs were obtained when the (100) tilted 10 degrees off toward [111] GaAs substrate was used. Besides, the oxygen content in N++-GaAs and P++-AlGaAs layers grown on the 10 degrees off GaAs substrates was reduced due to the reduction of sticking coefficient and number of anisotropic sites. (C) 2010 American Institute of Physics. [doi:10.1063/1.3525158]
Electrical Characterization of Al(2)O(3)/n-InAs Metal-Oxide-Semiconductor Capacitors With Various Surface Treatments
(2011-06-01)
Trinh, H. D.
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Brammertz, G.
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Chang, E. Y.
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Kuo, C. I.
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Lu, C. Y.
Ex situ sulfide and HCl wet chemical treatments in conjunction with in situ trimethyl aluminum (TMA) pretreatment were performed before the deposition of Al(2)O(3) on n-InAs surfaces. X-ray photoelectron spectroscopy analyses show a significant reduction of InAs native oxides after different treatments. The capacitance-voltage C-V characterization of Al(2)O(3)/n-InAs structures shows that the frequency dispersion in the accumulation regime is small (< 0.75%/dec) and does not seem to be significantly affected by the different surface treatments, whereas the latter improves depletion and inversion behaviors of the n-channel metal-oxide-semiconductor capacitors. The interface trap density profiles extracted from the simulation mainly show donorlike interface states inside the InAs band gap and in the lower part of the conduction band. The donorlike traps inside the InAs band gap and in the lower part of the conduction band were significantly reduced by using wet-chemical-plus-TMA treatments, in agreement with C-V characteristics.
Electrical Characterization of Al2O3/n-InAs Metal-Oxide-Semiconductor Capacitors With Various Surface Treatments
(2011-06-01)
Trinh, H. D.
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Brammertz, G.
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Chang, E. Y.
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Kuo, C. I.
;
Lu, C. Y.
Ex situ sulfide and HCl wet chemical treatments in conjunction with in situ trimethyl aluminum (TMA) pretreatment were performed before the deposition of Al2O3 on n-InAs surfaces. X-ray photoelectron spectroscopy analyses show a significant reduction of InAs native oxides after different treatments. The capacitance-voltage C-V characterization of Al2O3/n-InAs structures shows that the frequency dispersion in the accumulation regime is small (< 0.75%/dec) and does not seem to be significantly affected by the different surface treatments, whereas the latter improves depletion and inversion behaviors of the n-channel metal-oxide-semiconductor capacitors. The interface trap density profiles extracted from the simulation mainly show donorlike interface states inside the InAs band gap and in the lower part of the conduction band. The donorlike traps inside the InAs band gap and in the lower part of the conduction band were significantly reduced by using wet-chemical-plus-TMA treatments, in agreement with C-V characteristics.
Growth Parameters Optimization of GaN High Electron Mobility Transistor Structure on Silicon Carbide Substrate
(2014-01-01)
Wong, Y. Y.
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Huang, S. C.
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Huang, W. C.
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Lumbantoruan, F.
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Chiu, Y. S.
High electron mobility transistors heterostructures of AlGaN/GaN were grown by metalorganic chemical vapor deposition system on silicon carbide substrate. The growth parameters such as AlN buffer thickness, AlN spacer growth time and Al content in AlGaN barrier layer were optimized. Moreover, the effects of chamber pressure and V/III ratio at the initial growth state of GaN on film crystal quality were also investigated. The optimized AlGaN/GaN heterostructure has AlN buffer thickness of 120 nm, AlN spacer growth time of 10 s and Al content of 28% in the barrier layer. Furthermore, as a result of using higher chamber pressure and lower V/III, both the GaN crystal quality and electron mobility in the AlGaN/GaN were also significantly improved. After the growth parameter optimization, the GaN (002) and (102) planes exhibited X-ray rocking curve widths of 209 arcsec and 273 arcsec, respectively. Besides, the AlGaN/GaN structure also has an electron mobility of 1832 cm(2)/V-s and a sheet electron density of 1.08 10(13) cm(-2), which yielding a sheet resistance of 316 Omega/sq.
Low Current Collapse and Low Leakage GaN MIS-HEMT Using AlN/SiN as Gate Dielectric and Passivation Layer
(2014)
Liu, S. C.
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Wong, Y. Y.
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Lin, Y. C.
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Chang, E. Y.
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材料科學與工程學系
An effective passivation and gate insulator with low current collapse and improved dynamic ON-state resistance (R-ON) for GaN MIS-HEMT is demonstrated in this work. The structure of passivation and gate insulator is fabricated by 4-nm SiN as the first passivation layer and 1-nm AlN. The bilayer AlN/SiN structure integrates the advantages of SiN and AlN. SiN passivation has been proved to effectively reduce GaN surface states. AlN has high bandgap of similar to 6.2 eV which can suppress leakage current. Hence, the unfavorable effects such as trapping effect and leakage current which will induce current collapse and are effectively suppressed by using AlN/SiN bilayer thin film. A GaN MIS-HEMT with AlN/SiN passivation and gate dielectric exhibits improved I. V characteristics, low leakage current, low current collapse, and improved dynamic RON at high quiescent drain bias of 100 V.
Study of the thermal property of copper oxide nanowires
(2009-01-01)
Dee, C. F.
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Wong, Y. Y.
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Lim, K. P.
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Majlis, B. Y.
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材料科學與工程學系
As a high potential candidate for field-emission emitters, gas sensors, high-critical temperature superconductors, copper oxide NWs have been intensively studied in the synthesized methods, electrical properties and chemical properties. However, there are not many literatures report on the thermal property of them. It is important for one to understand the thermal behavior in order to justify the failure limit of the material especially in nanoscale. In this paper, copper oxide NWs synthesized through direct heating in atmospheric ambient were rapidly annealed in nitrogen ambient at different temperature to check the critical thermal failure point where the free standing copper oxide NWs start to collapse. It was found that copper oxide NWs with diameters around 100 nm started to collapse after 30 minutes of annealing in the nitrogen ambient at 300 degrees C due to the thermal shock incurred by rapid annealing. Increase in temperature will cause the NWs with bigger diameters start to fail. NWs in same diameter range will be able to withstand the temperature up to several hours if no thermal shock is induced. This was happening even when the wires were heated in a higher temperature of 600 degrees C. This result is important for copper oxide NWs when they are incorporated into the other heat sensitive device. The results are important for justifying the failure behavior for devices based on copper oxide NWs.
The influences of surface treatment and gas annealing conditions on the inversion behaviors of the atomic-layer-deposition Al(2)O(3)/n-In(0.53)Ga(0.47)As metal-oxide-semiconductor capacitor
(2010-07-26)
Trinh, H. D.
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Chang, E. Y.
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Wu, P. W.
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Wong, Y. Y.
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Chang, C. T.
The inversion behaviors of atomic-layer-deposition Al(2)O(3)/n-In(0.53)Ga(0.47)As metal-oxide-semiconductor capacitors are studied by various surface treatments and postdeposition annealing using different gases. By using the combination of wet sulfide and dry trimethyl aluminum surface treatment along with pure hydrogen annealing, a strong inversion capacitance-voltage (C-V) response is observed, indicating a remarkable reduction in interface trap state density (D(it)) at lower half-part of In(0.53)Ga(0.47)As band gap. This low D(it) was confirmed by the temperature independent C-V stretch-out and horizontal C-V curves. The x-ray photoelectron spectroscopy spectra further confirm the effectiveness of hydrogen annealing on the reduction of native oxides. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467813]
The influences of surface treatment and gas annealing conditions on the inversion behaviors of the atomic-layer-deposition Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitor
(2010-07-26)
Trinh, H. D.
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Chang, E. Y.
;
Wu, P. W.
;
Wong, Y. Y.
;
Chang, C. T.
The inversion behaviors of atomic-layer-deposition Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitors are studied by various surface treatments and postdeposition annealing using different gases. By using the combination of wet sulfide and dry trimethyl aluminum surface treatment along with pure hydrogen annealing, a strong inversion capacitance-voltage (C-V) response is observed, indicating a remarkable reduction in interface trap state density (D-it) at lower half-part of In0.53Ga0.47As band gap. This low D-it was confirmed by the temperature independent C-V stretch-out and horizontal C-V curves. The x-ray photoelectron spectroscopy spectra further confirm the effectiveness of hydrogen annealing on the reduction of native oxides. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467813]