Browsing by Author "Nguyen, Hong-Quan"

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Direct growth of a 40 nm InAs thin film on a GaAs/Ge heterostructure by metalorganic chemical vapor deposition
(2014-09-01)
Yu, Hung-Wei
;
Wang, Tsun-Ming
;
Nguyen, Hong-Quan
;
Wong, Yuen-Yee
;
Tu, Yung-Yi
In this paper, the authors directly grew an InAs thin film (40 nm) by metalorganic chemical vapor deposition on GaAs/Ge substrates by using flow-rate modulation epitaxy with an appropriate V/III ratio. The growth of a high-quality InAs thin film with periodic 90 degrees misfit dislocations was related to a uniform monolayer In atom distribution at the InAs/GaAs interface. The In monolayer effectively minimized the difference between surface energy and strain energy, producing a stable interface during material growth. The authors also found that a tightly controlled V/III ratio can improve the quality of the InAs islands on the GaAs/Ge heterostructures, though it is not the key factor in InAs thin-film growth. (C) 2014 American Vacuum Society.
Effect of V/III Ratios on Surface Morphology in a GaSb Thin Film Grown on GaAs Substrate by MOCVD
(2014-01-01)
Hsiao, Chih-Jen
;
Liu, Chun-Kuan
;
Huynh, Sa-Hoang
;
Minh, Thien-Huu Ha
;
Yu, Hung-Wei
The epitaxial growth of GaSb thin film with different V/III ratios on high-lattice-mismatched GaAs (001) substrates by metal organic chemical vapor deposition (MOCVD) was investigated. Under optimal V/III ratio of 2.5, we found that there are many periodic 90 degrees interfacial misfit dislocation (IMF) arrays existing at the GaAs/GaSb interface. The surface roughness is about 3.6nm, 2.2nm, 3.8nm, respectively while different V/III ratios (1.25, 2.5, 5) were adopted. These results demonstrated that the hill-and valley structure on the surface of GaSb/GaAs heterostructure can be effectively improved, and formed smooth surface morphology.
Effects of Wet Chemical and Trimethyl Aluminum Treatments on the Interface Properties in Atomic Layer Deposition of Al(2)O(3) on InAs
(2010-11-01)
Trinh, Hai-Dang
;
Chang, Edward Yi
;
Wong, Yuen-Yee
;
Yu, Chih-Chieh
;
Chang, Chia-Yuan
The reduction of native oxides on an In As surface using various wet and dry chemical treatments including hydrochloric acid (HCl) treatment sulfide treatment and in situ trimethyl aluminum (TMA) treatment before the atomic layer deposition (ALD) of Al(2)O(3) on In As is studied X ray photoelectron spectrum (XPS) results show that the effect of surface cleaning by TMA was apparent almost after the first pulse but that TMA cleaning is not as effective as wet chemical surface cleaning The combination of wet chemical treatment and TMA pretreatment is the most effective method for In As surface cleaning as indicated by the XPS analysis Capacitance-voltage (C-V) and current density-voltage (J-V) characteristics on metal-oxide-semiconductor capacitance (MOSCAP) structures were also investigated to evaluate the Al(2)O(3)/n In As interface quality after different surface treatments and the results are consistent with the XPS analysis (C) 2010 The Japan Society of Applied Physics
Effects of Wet Chemical and Trimethyl Aluminum Treatments on the Interface Properties in Atomic Layer Deposition of Al2O3 on InAs
(2010-11-01)
Trinh, Hai-Dang
;
Chang, Edward Yi
;
Wong, Yuen-Yee
;
Yu, Chih-Chieh
;
Chang, Chia-Yuan
The reduction of native oxides on an In As surface using various wet and dry chemical treatments including hydrochloric acid (HCl) treatment sulfide treatment and in situ trimethyl aluminum (TMA) treatment before the atomic layer deposition (ALD) of Al2O3 on In As is studied X ray photoelectron spectrum (XPS) results show that the effect of surface cleaning by TMA was apparent almost after the first pulse but that TMA cleaning is not as effective as wet chemical surface cleaning The combination of wet chemical treatment and TMA pretreatment is the most effective method for In As surface cleaning as indicated by the XPS analysis Capacitance-voltage (C-V) and current density-voltage (J-V) characteristics on metal-oxide-semiconductor capacitance (MOSCAP) structures were also investigated to evaluate the Al2O3/n In As interface quality after different surface treatments and the results are consistent with the XPS analysis (C) 2010 The Japan Society of Applied Physics
Ge epitaxial films on GaAs (100), (110), and (111) substrates for applications of CMOS heterostructural integrations
(2013-03-01)
Tang, Shih-Hsuan
;
Kuo, Chien-I
;
Trinh, Hai-Dang
;
Chang, Edward Yi
;
Nguyen, Hong-Quan
Epitaxial Ge films were grown on GaAs (100), (110), and (111) substrates by using ultra-high vacuum chemical vapor deposition and studied with various methods. The incubation times and growth rates were quite different for these three GaAs substrates because the surface arsenic coverage on GaAs and hydrogen desorption energy on Ge are different for each orientation. High-resolution x-ray diffraction measurements, direct band-gap emission of photoluminescence measurements, and cross-sectional transmission electron microscopy showed that the Ge films had high crystal quality, low defect density, and sharp Ge/GaAs interfaces. In this study, atomic force microscopy analysis found that the Ge films grow on GaAs (100) and (111) via the Frank van der Merwe mode, while the Ge film grows on GaAs (110) via the Volmer-Weber mode at the initial growth stage, which can be explained by the thermodynamic theory of capillarity. Interestingly, when the thickness of the Ge film on the GaAs (110) substrate increases to similar to 220 nm, the 3D Ge islands merge and form a smooth surface (rms roughness of 0.3 nm), which is useful for devices. The authors also fabricated Ge metal-oxide-semiconductor capacitors (MOSCAPs) on GaAs (100) and (110) substrates. Both Ge/GaAs (100) and Ge/GaAs (110) MOSCAPs exhibit good capacitance-voltage responses with strong inversion behaviors, which means the grown material has reached device quality. The Ge/GaAs (110) structure especially offers optimal integration of Ge pMOSFETs on GaAs substrates because Ge (110) has a high hole mobility compared with Ge (100) and (111). (C) 2013 American Vacuum Society. [http://dx.doi.org/10.1116/1.4789427]
Structural and photoluminescence investigation on the hot-wire assisted plasma enhanced chemical vapor deposition growth silicon nanowires
(2012-06-01)
Chong, Su Kong
;
Goh, Boon Tong
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Wong, Yuen-Yee
;
Nguyen, Hong-Quan
;
Do, Hien
High density of silicon nanowires (SiNWs) were synthesized by a hot-wire assisted plasma enhanced chemical vapor deposition technique. The structural and optical properties of the as-grown SiNWs prepared at different rf power of 40 and 80 W were analyzed in this study. The SiNWs prepared at rf power of 40 W exhibited highly crystalline structure with a high crystal volume fraction. X-C of similar to 82% and are surrounded by a thin layer of SiOx. The NWs show high absorption in the high energy region (E > 1.8 eV) and strong photoluminescence at 1.73 to 2.05 eV (red-orange region) with a weak shoulder at 1.65 to 1.73 eV (near IR region). An increase in rf power to 80 W reduced the X-C to similar to 65% and led to the formation of nanocrystalline Si structures with a crystallite size of < 4 nm within the SiNWs. These NWs are covered by a mixture of uncatalyzed amorphous Si layer. The SiNWs prepared at 80 W exhibited a high optical absorption ability above 99% in the broadband range between 220 and similar to 1500 nm and red emission between 1.65 and 1.95 eV. The interesting light absorption and photoluminescence properties from both SiNWs are discussed in the text. (C) 2012 Elsevier B.V. All rights reserved.
The Effect of CdS QDs Structure on the InGaP/GaAs/Ge Triple Junction Solar Cell Efficiency
(2014-03-01)
Chung, Chen-Chen
;
Tran, Binh Tinh
;
Han, Hau-Vei
;
Ho, Yen-Teng
;
Yu, Hung-Wei
This work describes optical and electrical characteristics of InGaP/GaAs/Ge triple-junction (T-J) solar cells with CdS quantum dots (QDs) fabricated by a novel chemical solution. With the anti-reflective feature at long wavelength and down-conversion at UV regime, the CdS quantum dot effectively enhance the overall power conversion efficiency more than that of a traditional GaAs-based device. Experimental results indicate that CdS quantum dot can enhance the short-circuit current by 0.33 mA/cm(2), which is observed for the triple-junction solar cells with CdS QDs of about 3.5 nm in diameter. Moreover, the solar cell conversion efficiency is improved from 28.3% to 29.0% under one-sun AM 1.5 global illumination I-V measurement.
The growth of pine-leaf-like hierarchical SnO2 nanostructures
(2014-01-01)
Dee, Chang Fu
;
Tiong, Teck Yaw
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Varghese, Binni
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Sow, Chorng-Haur
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Wong, Yuan-Yee
Pine-leaf-like SnO2 hierarchical nanostructures (NSs) were grown by a two-step vapour transport deposition process with a combination of vapour-solid and vapour-liquid-solid mechanisms at the primary and secondary processes, respectively. This type of hierarchical structure consisted of SnO2 trunk with homo-branching nanowires (NWs). The branched NWs connected the trunk NWs at included angles of 56 degrees and 90 degrees for two different types of hierarchical NSs. Based on the thermodynamic calculation, the formation of branched NWs at those angles are all energetically favourable.
The growth of pine-leaf-like hierarchical SnO2 nanostructures
(2014-01-01)
Dee, Chang Fu
;
Tiong, Teck Yaw
;
Varghese, Binni
;
Sow, Chorng-Haur
;
Wong, Yuan-Yee
Pine-leaf-like SnO2 hierarchical nanostructures (NSs) were grown by a two-step vapour transport deposition process with a combination of vapour-solid and vapour-liquid-solid mechanisms at the primary and secondary processes, respectively. This type of hierarchical structure consisted of SnO2 trunk with homo-branching nanowires (NWs). The branched NWs connected the trunk NWs at included angles of 56 degrees and 90 degrees for two different types of hierarchical NSs. Based on the thermodynamic calculation, the formation of branched NWs at those angles are all energetically favourable.
Ti/Al/Ti/Ni/Au ohmic contacts on AlGaN/GaN high electron mobility transistors with improved surface morphology and low contact resistance
(2014-01-01)
Chiu, Yu-Sheng
;
Lin, Tai-Ming
;
Nguyen, Hong-Quan
;
Weng, Yu-Chen
;
Nguyen, Chi-Lang
Optimizing surface morphology of ohmic contacts on GaN high electron mobility transistors continues to be a challenge in the GaN electronics industry. In this study, a variety of metal schemes were tested under various annealing conditions to obtain contacts with optimal qualities. A Ti/Al/Ti/Ni/Au (20/120/40/60/50 nm) metal scheme demonstrated the lowest contact resistance (R-c) and a smooth surface morphology, and the mechanisms were investigated by materials analysis. A Ti/Al/Ti/Ni/Au metal scheme with optimized Ti and Ni thicknesses can result in formation of a larger proportion of Al-Ni intermetallics and a continuous TiN interlayer, which results in smooth surface and low R-c. (C) 2014 American Vacuum Society.