Browsing by Author "Hsiao, Chih-Jen"

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Effect of Different Tunnel diodes on The Efficiency of Multi-junction III-V Solar cells
(2014-01-01)
Yu, Hung-Wei
;
Hong-Quan Nguyen
;
Chung, Chen-Chen
;
Hsu, Ching-Hsiang
;
Hsiao, Chih-Jen
InGaP/GaAs dual-junction solar cells with different tunnel diodes (TDs) grown on misoriented GaAs substrates are investigated. It is found that the solar cells with P++-AlGaAs/N++-GaAs TDs grown on 10 degrees off GaAs substrates show a higher external quantum efficiency (EQE) but also generate a higher peak current density (J(peak)) than the solar cells with P++-GaAs/N++-InGaP TDs grown on 10 degrees off GaAs substrates. Furthermore, 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. The conversion efficiency of InGaP/GaAs dual-junction solar cell with N++-GaAs/P++-AlGaAs TD grown on the (100) tilted 10 degrees off toward (111) GaAs substrate is close to 20%.
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
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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.
Growth and Crystal Structure Investigation of InAs/GaSb Heterostructure Nanowires on Si Substrate
(2018-11-01)
Kakkerla, Ramesh Kumar
;
Hsiao, Chih-Jen
;
Anandan, Deepak
;
Singh, Sankalp Kumar
;
Chang, Sheng-Po
We report gold-free growth of vertically aligned InAs/GaSb heterostructure nanowires (NWs) on Si(111) substrate by metal organic chemical vapor deposition technique. The effect of growth temperature on morphology and growth rate for InAs and InAs/GaSb heterostructure NWs were investigated. A combination of high material flow rates and optimum temperature (600 degrees C) has given better crystal quality of InAs nanowires. The morphology and shell thickness of NWs as observed by scanning electron microscope and transmission electron microscope (TEM) measurements 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 at certain growth temperatures. Crystal structure of InAs and InAs/GaSb heterostructure NWs was analyzed by high-resolution TEM and fast Fourier transform analysis. Using good crystalline InAs core grown at optimized growth temperature (600 degrees C), GaSb shell has been grown without any misfit dislocations at the core-shell interface. Basic electrical properties have been measured by forming ohmic contacts. I-V characteristics exhibit linear response indicating good ohmic behavior. These results show good control over InAs NWs growth, the GaSb shell thickness, and its crystal quality, which are essential for future nanoelectronic devices such as tunneling FET.
Growth and Crystal Structure Investigation of Self-catalyst InAs/GaSb Heterostructure Nanowires on Si substrate
(2017-01-01)
Kakkerla, Ramesh Kumar
;
Hsiao, Chih-Jen
;
Anandan, Deepak
;
Singh, Sankalp Kumar
;
Chang, Edward Yi
We demonstrate the self-catalyst (SC) growth of vertically aligned InAs and InAs/GaSb heterostructure nanowires on Si(111) substrate by Metal Organic Chemical Vapor Deposition (MOCVD). The effect of growth temperature on morphology and growth rate for SC InAs and InAs/GaSb heterostructure nanowires (NWs) were investigated. Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) measurements revealed 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 SC InAs NW core at certain growth temperatures. Crystal structure of InAs/GaSb heterostructure nanowires was also discussed. These results show that the control over SC InAs NWs growth, the GaSb shell thickness and it's crystal quality was achieved which is essential for future nano electronic devices such as TFET.
Growth of ultrathin GaSb layer on GaAs using metal-organic chemical vapor deposition with Sb interfacial treatment
(2016-09)
Hsiao, Chih-Jen
;
Minh-Thien-Huu Ha
;
Hsu, Ching-Yi
;
Lin, Yueh-Chin
;
Chang, Sheng-Po
GaSb epitaxial layers were directly grown on GaAs substrates by metal-organic chemical vapor deposition involving Sb interfacial treatment with optimized growth temperature and V/III ratio. The interfacial treatment effectively reduces the surface energy and strain energy difference, resulting in a quasi-2D growth mode. When the GaSb layer was grown at 520 degrees C, the strain induced by lattice mismatch was accommodated by 90 degrees dislocations with a period of 5.67 nm. By optimizing the V/III ratio, the surface roughness of the ultrathin GaSb/GaAs heterostructure was reduced, resulting in a reduced carrier scattering and improved electronic properties. (C) 2016 The Japan Society of Applied Physics
High color-stability for white organic light emitting devices by using phosphorescent sensitizer fluorescent
(2010)
Juang, Fuh-Shyang
;
Hong, Lin-Ann
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Hsiao, Chih-Jen
;
Wang, Shun-Hsi
;
Ho, Meng-Huan
High color-stability white OLEDs can be achieved by replacing red fluorescent dopant (DCJTB) with yellow dopant (EY-53) in phosphor-sensitized emitter and optimizing the interlayer (CBP) thickness. Device shows the E.Q.E. of 8.2%, the efficiencies of 21.5 cd/A and 8.1 lm/VV with CIE (0.40, 0.46) at 20 mA/cm(2). The shift of ClExy down to (-0.001,-0.001) at a current density of 20 and 200 mA/cm2.
InGaAs Junctionless FinFETs With Self-Aligned Ni-InGaAs S/D
(2018-01-01)
Chang, Po-Chun
;
Hsiao, Chih-Jen
;
Lumbantoruan, Franky Juanda
;
Wu, Chia-Hsun
;
Lin, Yen-Ku
In this paper, the InGaAs junctionless (JL) FinFET with notable electrical performance is demonstrated. The device with W-fin down to 20 nm, EOT of 2.1 nm, and L-G = 60 nm shows high I-ON = 188 mu A/mu m at V-DD = 0.5 V and I-OFF = 100 nA/mu m, I-ON/I-OFF = 5 x 10(5), DIBL = 106 mV/V and SS = 96 mV/dec. The device also exhibits a decent extrinsic transconductance (G(m)) of 1142 mu S/mu m at V-DS of 0.5 V. This high performance is attributed to the moderate doping concentration to ensure the channel carriers could be effectively depleted and the low R-SD realized by self-aligned Ni-InGaAs alloy S/D. Furthermore, we also examine the temperature dependence of the main electrical parameters of the JL transistor.
Performance improvement of highly mismatched GaSb layers on GaAs by interfacial-treatment-assisted chemical vapor deposition
(2017-01)
Hsiao, Chih-Jen
;
Minh-Thien-Huu Ha
;
Liu, Chun-Kuan
;
Hong-Quan Nguyen
;
Yu, Hung-Wei
Strain-relieved GaSb quantum dots on GaAs can be achieved by either periodic interfacial misfit (IMF) or the conventional Stranski-Krastanov (SK) growth modes by changing the growth parameters. In this study, the Sb interfacial treatment was employed to improve the GaSb crystal quality including low defect density, smooth surface morphology, and high hole mobility. This technique yields two-dimensional (2D) islands with a height as low as 1.7 nm and width up to 190 nm in the IMF growth mode. In contrast to the interfacial treatments conventionally employed in the initial strain relaxation of GaSb/GaAs hererostructure, the Sb treatment promotes the formation of strong Ga-Sb bonds on the surface of the grown island, which effectively reduces the interfacial free energy and thus promotes the formation of 2D islands. With the Sb interfacial treatment, a high-relaxation 100-nm GaSb epilayer was grown on the GaAs substrate, the epilayers was strain relaxed and exhibited enhanced electrical properties with a high hole mobility of similar to 667 cm(2) V-1 s(-1) and with superior optical properties as evidenced by the photoluminescence B-line peak. The results of this study demonstrate an effective interfacial-treatment growth technique to relax the initial strain for the highly mismatched GaSb layers grown on a GaAs substrate.
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
;
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.