Browsing by Author "Yu, Hung Wei"

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Crystal phase control in self-catalyzed InSb nanowires using basic growth parameter V/III ratio
(2019-09-15)
Anandan, Deepak
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Nagarajan, Venkatesan
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Kakkerla, Ramesh Kumar
;
Yu, Hung Wei
;
Ko, Hua Lun
In this work, the influence of V/III ratio on self-catalyzed InSb nanowire (NW) crystal structure is investigated using metal organic chemical vapor deposition. The effective balance of V/III ratio determines the change of InSb NW crystal structure from zincblende to wurtzite. Particularly, as group-V molar flow varies from 6.4 x 10(-5) to 8.0 x 10(-5) mol/min, wurtzite segment length of InSb NW increases from 16 +/- 9 nm to 89 +/- 9 nm, whereas zincblende crystal phase is observed for other molar flows. We interpret the observed phase transition to a lower surface energy of In-Sb alloy droplet than pure In-droplet, which makes triple phase line nucleation energetically favorable. This study gives insight on single growth parameter (V/III ratio) change to the InSb NW crystal control, such a technique is essential to selectively tune the crystal phase of single NW for various applications.
Crystal structure control of Au-free InAs and InAs/GaSb heterostucture nanowires grown on Si (111) by metal-organic chemical vapor deposition
(2019-01-01)
Kakkerla, Ramesh Kumar
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Anandan, Deepak
;
Singh, Sankalp Kumar
;
Yu, Hung Wei
;
Lee, Ching-Ting
In this letter, the growth of gold-free GaSb on various InAs nanowire (NW) crystal structures using metal-organic chemical vapor deposition is demonstrated. The GaSb was grown radially and axially on wurtzite (WZ), zinc-blend (ZB) and polytype (mixture of WZ and ZB) InAs NWs. The effect of the various InAs crystal structures on GaSb was studied. This study demonstrates the control of the crystal growth of InAs and InAs/GaSb heterostructure NWs through the optimization of growth parameters and crystal transfer from core to shell, such techniques are necessary for the growth of NWs for future nanoelectronic device applications, such as TFET. (C) 2018 The Japan Society of Applied Physics
Effect of Two-Step Metal Organic Chemical Vapor Deposition Growth on Quality, Diameter and Density of InAs Nanowires on Si (111) Substrate
(2018-02-01)
Yu, Hung Wei
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Anandan, Deepak
;
Hsu, Ching Yi
;
Hung, Yu Chih
;
Su, Chun Jung
High-density (similar to 80/um(2)) vertical InAs nanowires (NWs) with small diameters (similar to 28 nm) were grown on bare Si (111) substrates by means of two-step metal organic chemical vapor deposition. There are two critical factors in the growth process: (1) a critical nucleation temperature for a specific In molar fraction (approximately 1.69 x 10(-5) atm) is the key factor to reduce the size of the nuclei and hence the diameter of the InAs NWs, and (2) a critical V/III ratio during the 2nd step growth will greatly increase the density of the InAs NWs (from 45 mu m(-2) to 80 mu m(-2)) and at the same time keep the diameter small. The high-resolution transmission electron microscopy and selected area diffraction patterns of InAs NWs grown on Si exhibit a Wurtzite structure and no stacking faults. The observed longitudinal optic peaks in the Raman spectra were explained in terms of the small surface charge region width due to the small NW diameter and the increase of the free electron concentration, which was consistent with the TCAD program simulation of small diameter (< 40 nm) InAs NWs.
Growth of foreign-catalyst-free vertical InAs/InSb heterostructure nanowires on Si (111) substrate by MOCVD
(2019-01-15)
Anandan, Deepak
;
Kakkerla, Ramesh Kumar
;
Yu, Hung Wei
;
Ko, Hua Lun
;
Nagarajan, Venkatesan
In this study, growth of Au-free InAs/InSb vertical heterostructure (HS) nanowires (NWs) on highly lattice mismatched Si (1 1 1) substrate by metal organic chemical vapor deposition (MOCVD) is demonstrated. Careful selections of InSb growth parameters lead to In-rich growth regime such that direct impingement of growth precursors on top of grown InAs NW (self-assembled) stems result in axial InSb HSs nucleation on InAs stems. The observed indium (In) droplet on InSb HS NW tip shows that InSb HS growth followed a self-catalyzed growth mechanism. InSb HS axial growth rate and morphology are controlled by growth temperature and growth time. A small change in the growth parameters significantly affects In particle accumulation, particle size and its chemical composition, and thus affects the InSb nucleation on the stem. Especially, it is found that (i) growth time of less 10 min yields vertical InSb HS NW on the top of the InAs stem, (ii) as the growth time increases above 10 min, the growth turned to be InSb wrapped InAs/InSb core-shell HS due to coaxial lateral growth. High resolution transmission electron microscopy (HRTEM) study reveals that all the InSb HSs exhibit pure zinc-blende (ZB) crystal structure. The results presented here provide significant guidelines for external catalyst-free InAs/InSb HS NW growth using MOCVD on silicon (Si) substrate for various optoelectronics and electronics applications.
Growth of high-quality In0.28Ga0.72Sb/AlSb/GaSb/GaAs heterostructure by metalorganic chemical vapor deposition for single-channel Sb-based complementary metal-oxide-semiconductor applications
(2017-07-01)
Huynh, Sa Hoang
;
Ha, Minh Thien Huu
;
Do, Huy Binh
;
Nguyen, Tuan Anh
;
Yu, Hung Wei
The growth of high-quality In0.28Ga0.72Sb epilayer on an AlSb/GaSb/GaAs heterostructure by metalorganic chemical vapor deposition is demonstrated. The In0.28Ga0.72Sb epilayer has a fully relaxed surface roughness of similar to 1.0nm and a low threading dislocation density of similar to 6.2 x 10(6)cm(-2). The valence band offset (VBO) of 3.11 eV and conduction band offset (CBO) of 3.21 eV for an Al2O3/In0.28Ga0.72Sb interface extracted from X-ray photoemission spectroscopy data highlight its suitability for use in single-channel InGaSb-based complementary metal-oxide-semiconductor (CMOS) applications. The type-I straddling gap of an In0.28Ga0.72Sb/AlSb heterojunction with a VBO of 0.47 eV and CBO of 0.65 eV is also sufficient to prevent both electron and hole leakage currents in CMOS devices. (C) 2017 The Japan Society of Applied Physics
High-Quality 1 eV In(0.3)Ga(0.7)As on GaAs Substrate by Metalorganic Chemical Vapor Deposition for Inverted Metamorphic Solar Cell Application
(2011-07-01)
Hong Quan Nguyen
;
Chang, Edward Yi
;
Yu, Hung Wei
;
Lin, Kung Liang
;
Chung, Chen Chen
In(0.3)Ga(0.7)As layers were grown by metalorganic chemical vapor deposition using step graded buffer layers on different misoriented GaAs(001) substrates. Smooth-surface In(0.3)Ga(0.7)As film with a root mean square roughness of 1.9 nm was obtained with the growth temperature of 490 degrees C using a 10-step graded parabolic-like indium profile buffer layer on the surface with the 6 degrees-off cut toward the [111] direction. The threading dislocation density in the film was determined to be 1.2 x 10(6) cm(-2) by transmission electron microscopy. The photoluminescence results obtained at 300 and 77K indicate that very low recombination centers existed in the epilayer. (C) 2011 The Japan Society of Applied Physics
High-Quality 1 eV In0.3Ga0.7As on GaAs Substrate by Metalorganic Chemical Vapor Deposition for Inverted Metamorphic Solar Cell Application
(2011-07-01)
Hong Quan Nguyen
;
Chang, Edward Yi
;
Yu, Hung Wei
;
Lin, Kung Liang
;
Chung, Chen Chen
In0.3Ga0.7As layers were grown by metalorganic chemical vapor deposition using step graded buffer layers on different misoriented GaAs(001) substrates. Smooth-surface In0.3Ga0.7As film with a root mean square roughness of 1.9 nm was obtained with the growth temperature of 490 degrees C using a 10-step graded parabolic-like indium profile buffer layer on the surface with the 6 degrees-off cut toward the [111] direction. The threading dislocation density in the film was determined to be 1.2 x 10(6) cm(-2) by transmission electron microscopy. The photoluminescence results obtained at 300 and 77K indicate that very low recombination centers existed in the epilayer. (C) 2011 The Japan Society of Applied Physics
Impact of interfacial misfit dislocation growth mode on highly lattice-mismatched InxGa1-xSb epilayer grown on GaAs substrate by metalorganic chemical vapor deposition
(2016-09-05)
Huynh, Sa Hoang
;
Minh Thien Huu Ha
;
Huy Binh Do
;
Quang Ho Luc
;
Yu, Hung Wei
Highly lattice-mismatch (over 8%) ternary InxGa1-xSb alloy directly grown on GaAs substrates was demonstrated by metalorganic chemical vapor deposition (MOCVD). The influence of growth parameters, such as growth temperature, indium vapor composition, and V/III ratio, on the film properties was investigated, and it was found that the growth temperature has the strongest effect on the surface morphology and the crystal quality of the InxGa1-xSb epilayer. An optimized growth temperature of similar to 590 degrees C and a V/III ratio of 2.5 were used for the growth of the InxGa1-xSb epilayer on GaAs that displays a lower surface roughness. High-resolution transmission electron microscopy micrographs exhibit that InxGa1-xSb epilayer growth on GaAs was governed by the interfacial misfit dislocation growth mode. Furthermore, the variation of the intermixing layer thickness at the InxGa1-xSb/GaAs heterointerface was observed. These results provide an information of growing highly lattice-mismatched epitaxial material systems by MOCVD growth process. Published by AIP Publishing.
InGaP/GaAs Dual-Junction Solar Cell with AlGaAs/GaAs Tunnel Diode Grown on 10 degrees off Misoriented GaAs Substrate
(2012-08-01)
Yu, Hung Wei
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Chung, Chen Chen
;
Wang, Chin Te
;
Hong Quan Nguyen
;
Binh Tinh Tran
InGaP/GaAs dual-junction solar cells with different tunnel diodes (TDs) grown on misoriented GaAs substrates are investigated. It is demonstrated that the solar cells with P++-AlGaAs/N++-GaAs TDs grown on 10 degrees off GaAs substrates not only show a higher external quantum efficiency (EQE) but also generate a higher peak current density (J(peak)) at higher concentration ratios (185 x) than the solar cells with P++-GaAs/N++-InGaP TDs grown on 6 degrees off GaAs substrates. Furthermore, the cell design with P++-AlGaAs/N++-GaAs TDs grown on 10 degrees off GaAs substrates does not generate a disordered InGaP epitaxial layer during material growth, and thus shows superior current-voltage characteristics. (c) 2012 The Japan Society of Applied Physics
Optimization of InAs/GaSb core-shell nanowire structure for improved TFET performance
(2019-10-01)
Singh, Sankalp Kumar
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Kakkerla, Ramesh Kumar
;
Joseph, H. Bijo
;
Gupta, Ankur
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Anandan, Deepak
The performance of InAs/GaSb core-shell nanowire TFET is systematically investigated for the effects of intrinsic device parameters such as channel doping, shell thickness, spacer length and source offset. Device ON-current (I-ON) was chosen as the key figure of merit. It is found that I-ON improves due to improved electrostatic control achieved by the TFET with optimum shell diameter. The maximum I-ON obtained for a shell thickness of 2 nm was 33.65 mu A/mu m and a Subthreshold Swing (SS) of 12.9 mV/decade with an I-ON/I-OFF ratio of 1.49 x 10(8) for our device. Device I-ON can be further improved by adding an optimum spacer at the source-channel junction. It was also found that device ON-current is almost constant and does not get much affected by having a larger shell offset.
Temperature effect on the growth of Au-free InAs and InAs/GaSb heterostructure nanowires on Si substrate by MOCVD
(2018-05-15)
Kakkerla, Ramesh Kumar
;
Anandan, Deepak
;
Hsiao, Chih-Jen
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Yu, Hung Wei
;
Singh, Sankalp Kumar
We demonstrate the growth of vertically aligned Au-free InAs and InAs/GaSb heterostructure nanowires on Si (1 1 1) substrate by Metal Organic Chemical Vapor Deposition (MOCVD). The effect of growth temperature on the morphology and growth rate of the InAs and InAs/GaSb heterostructure nanowires (NWs) is investigated. Control over diameter and length of the InAs NWs and the GaSb shell thickness was achieved by using growth temperature. As the GaSb growth temperature increase, GaSb radial growth rate increases due to the increase in alkyl decomposition at the substrate surface. Diffusivity of the adatoms increases as the GaSb growth temperature increase which results in tapered GaSb shell growth. Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) measurements revealed that the morphology and shell thickness can be tuned by the growth temperature. Electron microscopy also shows the formation of GaSb both in radial and axial directions outside the InAs NW core can be controlled by the growth temperature. This study demonstrates the control over InAs NWs growth and the GaSb shell thickness can be achieved through proper growth temperature control, such technique is essential for the growth of nanowire for future nano electronic devices, such as Tunnel FET. (C) 2018 Elsevier B.V. All rights reserved.
The Growth and Fabrication of High-Performance In0.5Ga0.5As Metal-Oxide-Semiconductor Capacitor on GaAs Substrate by Metalorganic Chemical Vapor Deposition Method.
(2012-01-01)
Hong Quan Nguyen
;
Hai Dang Trinh
;
Yu, Hung Wei
;
Hsu, Ching Hsiang
;
Chung, Chen Chen
Growth conditions have investigated for growing high quality In0.3Ga0.7As and In0.5Ga0.5As on GaAs substrate by metalorganic chemical vapor deposition method. Annihilation reactions between threading dislocations observed by transmission electron microscopy are experimental evidences to confirm threading dislocations had been blocked in InxGa1-xAs buffer layers. A high quality smooth surface In0.5Ga0.5As epi-film with threading dislocation density of 2x10(6) cm(-2) was achieved at growth temperature of 490 degrees C. Metal-oxide-semiconductor capacitor devices fabricated on In0.5Ga0.5As/GaAs perform nice capacitance-voltage response, with small frequency dispersion. The conductance contours indicate that the Fermi level moves freely to the lower part of the InGaAs bandgap without pinning.
Titanium dioxide-mediated resistive nanobiosensor for E. coli O157:H7
(2020-03-17)
Nadzirah, Sh.
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Hashim, U.
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Gopinath, Subash C. B.
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Parmin, N. A.
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Hamzah, Azrul Azlan
A titanium dioxide nanoparticle (TiO2 NP)-mediated resistive biosensor is described for the determination of DNA fragments of Escherichia coli O157:H7 (E. coli O157:H7). The sol-gel method was used to synthesize the TiO2 NP, and microlithography was applied to fabricate the interdigitated sensor electrodes. Conventional E. coli DNA detections are facing difficulties in long-preparation-and-detection-time (more than 3 days). Hence, electronic biosensor was introduced by measuring the current-voltage (I-V) DNA probe without amplification of DNA fragments. The detection scheme is based on the interaction between the electron flow on the sensor and the introduction of negative charges from DNA probe and target DNA. The biosensor has a sensitivity of 1.67 x 10(13) omega/M and a wide analytical range. The limit detection is down to 1 x 10(-11) M of DNA. The sensor possesses outstanding repeatability and reproducibility and is cabable to detect DNA within 15 min in a minute-volume sample (1 mu L).