Browsing by Author "Horng, Ray-Hua"

Now showing 1 - 20 of 64

1.48-kV enhancement-mode AlGaN/GaN high-electron-mobility transistors fabricated on 6-in. silicon by fluoride-based plasma treatment
(2016-05-01)
Yeh, Chih-Tung
;
Wang, Wei-Kai
;
Shen, Yi-Siang
;
Horng, Ray-Hua
;
電機學院
Enhancement-mode AlGaN/GaN high-electron-mobility transistors (HEMTs) were fabricated on a Si substrate by fluorine plasma treatment without pre-etching. The threshold voltage shifted from % 8 to 2.3 V, effectively converting the depletion-mode HEMT to the enhancement-mode HEMT. The leakage current was reduced by two orders of magnitude by CF4 plasma treatment. The device exhibited a superior performance with a maximum drain saturation current of 210mA/mm at V-GS = 10V and a peak gain of 44.1mS/mm. A low off-state gate leakage current of 10(-6)mA/mm, ION/IOFF ratio of approximately 10(8), and high breakdown voltage of 1480V were obtained. (C) 2016 The Japan Society of Applied Physics
1.48-kV enhancement-mode AlGaN/GaN high-electron-mobility transistors fabricated on 6-in. silicon by fluoride-based plasma treatment
(2016-05)
Yeh, Chih-Tung
;
Wang, Wei-Kai
;
Shen, Yi-Siang
;
Horng, Ray-Hua
;
電機學院
Enhancement-mode AlGaN/GaN high-electron-mobility transistors (HEMTs) were fabricated on a Si substrate by fluorine plasma treatment without pre-etching. The threshold voltage shifted from % 8 to 2.3 V, effectively converting the depletion-mode HEMT to the enhancement-mode HEMT. The leakage current was reduced by two orders of magnitude by CF4 plasma treatment. The device exhibited a superior performance with a maximum drain saturation current of 210mA/mm at V-GS = 10V and a peak gain of 44.1mS/mm. A low off-state gate leakage current of 10(-6)mA/mm, ION/IOFF ratio of approximately 10(8), and high breakdown voltage of 1480V were obtained. (C) 2016 The Japan Society of Applied Physics
A New Material and Structures for Light-Emitting Thyristor Applications
(2018-07-01)
Chen, Ching-Ho
;
Jhen, Jia-Jhen
;
Wuu, Dong-Sing
;
Horng, Ray-Hua
;
電子工程學系及電子研究所
We have demonstrated that GaInP materials with GaP and distributed Bragg reflector (DBR) structures can be applied in light-emitting thyristors (LEThs) and depleted optical thyristors (DOTs). The GaP epitaxial film greatly improved the current spreading, so that the brightness of LEThs was also greatly improved. The luminous intensity increased by 70% at an injection current of 250 mA with the GaP epitaxial film, compared to the LEThs without a GaP film. Moreover, the DBR structure played a role to prevent the emission light from being absorbed by the opaque GaAs substrate. The DBR structure can improve the droop efficiency, reduce the operation voltage, and maintain the wavelength at high-current operation. The luminous intensity of LEThs with the 18-pairs DBR structure increased by 71% at an injection current of 900 mA, compared to LETh with only three-pairs DBR and GaP window structure. It also showed nonlinear s-shaped I-V characteristics as a function of the input light intensity. The turn-on voltages were significantly reduced, from 5.36 to 1.66 V, as the external optical input intensity changed from dark to light with 300 mW. Under certain conditions, it also showed standard diode curve characteristics; as a result, the LETh can also be used as a DOTs.
AlGaInP Red LEDs with Hollow Hemispherical Polystyrene Arrays
(2018-01-17)
Cheng, Wen-Ching
;
Huang, Shih-Yung
;
Chen, Yi-Jiun
;
Wang, Chia-Sheng
;
Lin, Hoang Yan
A hollow hemispherical polystyrene (HHPS) was fabricated to reduce total internal reflection in AlGaInP-based LEDs. At an injection current of 350 mA, the external quantum efficiencies of LED-I, LED-II, LED-III, and LED-IV are 20.92%, 24.65%, 27.28%, and 33.77% and the wall-plug efficiencies are 17.11%, 20%, 22.5%, and 27.33%, respectively. The enhanced performance is attributed to the light output power enhancement through the surface roughness, microlens-liked PS hemisphere, and scatter-liked HHPS array. In this paper, the rigorous coupled wave analysis (RCWA) numerical method was also conducted to demonstrate the HHPS array effectively enlarge the effective light cone.
AlGaN/GaN MOS-HEMTs with Corona-Discharge Plasma Treatment
(2017-05-01)
Yuan, Shuo-Huang
;
Chang, Feng-Yeh
;
Wuu, Dong-Sing
;
Horng, Ray-Hua
;
電子工程學系及電子研究所
The effects of a corona-discharge plasma treatment on the performance of an AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistor fabricated onto Si substrates were studied. The threshold voltage shifted from -8.15 to -4.21 V when the device was treated with an Al2O3 layer. The leakage current was reduced from 2.9 x 10(-5) to 4.2 x 10(-7) mA/mm, and the I-ON/I-OFF ratio increased from 8.3 x 10(6) to 7.3 x 10(8) using the corona-discharge plasma treatment, which exhibited an increase of about two orders of magnitude. The device exhibited excellent performance with a subthreshold swing of 78 mV/dec and a peak gain of 47.92 mS/mm at V-GS = 10 V.
An efficient and stable photoelectrochemical system with 9% solar-to-hydrogen conversion efficiency via InGaP/GaAs double junction
(2019-11-21)
Varadhan, Purushothaman
;
Fu, Hui-Chun
;
Kao, Yu-Cheng
;
Horng, Ray-Hua
;
He, Jr-Hau
Despite III-V semiconductors demonstrating extraordinary solar-to-hydrogen (STH) conversion efficiencies, high cost and poor stability greatly impede their practical implementation in photoelectrochemical (PEC) water splitting applications. Here, we present a simple and efficient strategy for III-V-based photoelectrodes that functionally and spatially decouples the light harvesting component of the device from the electrolysis part that eliminates parasitic light absorption, reduces the cost, and enhances the stability without any compromise in efficiency. The monolithically integrated PEC cell was fabricated by an epitaxial lift-off and transfer of inversely grown InGaP/GaAs to a robust Ni-substrate and the resultant photoanode exhibits an STH efficiency of similar to 9% with stability similar to 150 h. Moreover, with the ability to access both sides of the device, we constructed a fully-integrated, unassisted-wireless "artificial leaf" system with an STH efficiency of similar to 6%. The excellent efficiency and stability achieved herein are attributed to the light harvesting/catalysis decoupling scheme, which concurrently improves the optical, electrical, and electrocatalytic characteristics.
Band alignment of In2O3/beta-Ga2O3 interface determined by X-ray photoelectron spectroscopy
(2018-07-16)
Sun, Shun-Ming
;
Liu, Wen-Jun
;
Wang, Yong-Ping
;
Huan, Ya-Wei
;
Ma, Gan
The energy band alignment of the atomic-layer-deposited In2O3/beta-Ga2O3((2) over bar 10) interface is evaluated by X-ray photoelectron spectroscopy. The X-ray diffraction pattern reveals that the In2O3 film grown at 160 degrees C is amorphous, while it becomes polycrystalline at a higher deposition temperature of 200 degrees C. The bandgaps, determined by reflection electron energy loss spectroscopy, are 4.65, 3.85, and 3.47 eV for beta-Ga2O3, polycrystalline In2O3, and amorphous In2O3, respectively. Both amorphous and polycrystalline In2O3/beta-Ga2O3 interfaces have Type I alignment. The conduction and valence band offsets at the polycrystalline (amorphous) In2O3/beta-Ga2O3 interface are 0.35 and 0.45 eV (0.39 and 0.79 eV), respectively. These observations suggest that polycrystalline In2O3 as an intermediate semiconductor layer is beneficial to the barrier reduction of metal/Ga2O3 contact. Published by AIP Publishing.
Band alignment of indium-gallium-zinc oxide/beta-Ga2O3((2)over-bar01) heterojunction determined by angle-resolved X-ray photoelectron spectroscopy
(2018-10-01)
Huan, Ya-Wei
;
Wang, Xing-Lu
;
Liu, Wen-Jun
;
Dong, Hong
;
Long, Shi-Bing
The energy band offsets between indium-gallium-zinc oxide (IGZO) and beta-Ga2O3 were examined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The Ga 2p spectra from the heterojunction contributed by the upper IGZO film and the beta-Ga2O3 substrate were deconvoluted into two sub-peaks with the binding energy difference of 0.3 eV, in good agreement with the theoretical model. Meanwhile, the bandgaps of IGZO and beta-Ga2O3 were measured to be 3.44 +/- 0.1 and 4.64 +/- 0.1 eV from the ultraviolet-visible (UV-vis) transmittance spectra. The valence and conduction band offsets between the IGZO and beta-Ga2O3 were consequently determined to be 0.49 +/- 0.05 and 0.71 +/- 0.1 eV, respectively. These findings reveal that IGZO is an attractive intermediate semiconductor layer (ISL) for reducing the electron barrier height at metal/Ga2O3 interfaces. (C) 2018 The Japan Society of Applied Physics
Characteristics of atomic layer deposition-grown zinc oxide thin film with and without aluminum
(2019-10-15)
Tseng, Ming-Chun
;
Wuu, Dong-Sing
;
Chen, Chi-Lu
;
Lee, Hsin-Ying
;
Chien, Cheng-Yu
Zinc oxide (ZnO) and Al-doped ZnO (AZO) thin films were deposited on glass substrates using atomic layer deposition. The Al composition of the AZO thin films was varied by controlling the Zn:Al cycle ratios. The ZnO and AZO thin films were characterized using atomic force microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and optical measurements. The electrical properties of the ZnO and AZO thin films were influenced by the Zn:Al cycle ratios. The resistivity of the AZO thin film decreased significantly, whereas the carrier concentration increased with the Al composition. As the Zn:Al cycle ratio increased, the AZO thin film achieved an average transmittance of > 85%.
Characterizations of Metal-Oxide-Semiconductor Field-Effect Transistors of ZnGaO Grown on Sapphire Substrate
(2017-03-01)
Shen, Yi-Siang
;
Wang, Wei-Kai
;
Horng, Ray-Hua
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Zinc gallate (ZnGaO) epilayers were grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition and fabricated into metal-oxide-semiconductor field-effect transistors (MOSFETs). The ZnGaO MOSFETs exhibited a complete channel pinch-off of the drain current for VGS < -4.43 V, high off-state breakdown voltage of 378 V, high I-ON/I-OFF ratio of 10(6), and low gate leakage current.
Chemical lift-off process for nitride LEDs from an Eco-GaN template using an AlN/strip-patterned-SiO2 sacrificial layer
(2017-03-01)
Horng, Ray-Hua
;
Hsueh, Hsu-Hung
;
Ou, Sin-Liang
;
Tsai, Chi-Tsung
;
Tsai, Tsung-Yen
In this research, a nitride light-emitting diode (LED) fabricated on an electroplated Cu substrate can be removed from a GaN/sapphire (Eco-GaN) template by conducting the chemical lift-off (CLO) process using an AlN/strip-patterned-SiO2 intermediate sacrificial layer. The regrowth GaN epilayer deposited on AlN/patterned SiO2/Eco-GaN can achieve a high crystal quality via the epitaxial lateral overgrowth process. To etch the patterned SiO2 and AlN layers, the HF and 80 degrees C-KOH solutions were used, respectively. Due to the use of low-temperature KOH solution, the GaN epilayer would suffer less damage during the CLO process, improving the reuse feasibility for the Eco-GaN template. Moreover, when the etching treatment was used for the AlN layer, a highly lateral etching rate of 0.5mmh(-1) was achieved. Compared to the conventional LED, the vertical-type LED/Cu substrate had a higher output power of 212mW (at 350mA). Based on our estimation, the output power of LED prepared on Cu substrate had an 86% improvement in comparison to that of conventional LED. Obviously, the good optoelectronic performance of the LED/Cu device can be obtained after performing the CLO process. Furthermore, the separated Eco-GaN template has high potential for reuse applications, indicating that this technique is helpful to the cost-effective LED fabrication.
Colloidal Quantum Dot Enhanced Dual-Junction Tandem Solar Cells
(2016-01-01)
Hsu, Shun-Chieh
;
Kao, Yu-Cheng
;
Han, Hau-Vei
;
Kuo, Hao-Chung
;
Horng, Ray-Hua
In this work, we demonstrate the the enhancement of two type hybrid QD dual-junction solar cell. The green QD520 sample, shows better performance than blue QD450 sample in current density and power conversion efficiency. The enhancement of short-circuit current and power conversion efficiency for green QD450 sample are 4.43% and 3.77% and the blue QD520 samples are 9.44% and 5.78%. For short wavelength, the enhancement can mainly be attributed to the photon downshift effect and antireflection, for long wavelength, it only the antireflection effect.
Comparison of Properties of Thin Film AlGaInP LEDs with Composite Metal and Si Substrates
(2019-11-25)
Sinha, ShreeKant
;
Feng, Hsiang-An
;
Chung, Cheng-Yu
;
Tu, Chia-Wei
;
Horng, Ray-Hua
N-side up thin-AlGaInP epilayers based on vertical light-emitting diodes (VLEDs) (light emitting area: 44 mil x 44 mil) with Si and composite metal (copper/Invar/copper; CIC) substrates were obtained by wafer bonding and epilayer transferring technologies. The coefficients of thermal expansion of the Si and CIC substrates were about 2.6 x 10(-6) /K and 6.1 x 10(-6) /K respectively. The coefficient of thermal expansion of CIC was matched to the GaAs substrate and AlGaInP epilayer. After the epilayer transferred to the CIC substrate, a small amount of bending occurred. The performance of the packaged LEDs/CIC was almost the same with that of LEDs/Si. The redshift phenomenon was from 623 to 643 nm for the CIC/LEDs while that of the LEDs/Si chip was from 625 to 643 nm with an injected current from 100 mA to 1 A and high output power (251 mW at 1 A) as compared to packaged LEDs/Si (299.5 mW at 1 A). The variation in light-emitting wavelengths of the LEDs/CIC was the same with that of the LEDs/Si. The distribution of the temperature of the LEDs on the CIC substrate was less than the LEDs on Si throughout the surface. The obtained data suggested that CIC could be extended instead of a Si substrate for high-power thin film LEDs applications. (c) The Author(s) 2019. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.
Deep-Ultraviolet LEDs Fabricated by Nanoimprinting
(2019-10-09)
Horng, Ray-Hua
;
Lai, Yan-Chung
;
Lai, Liang-Hsing
;
交大名義發表
;
電子工程學系及電子研究所
In this study, deep-ultraviolet 280-nm-wavelength light-emitting diodes (DUVLEDs) with a nanopatterned sapphire substrate (NPSS) were fabricated using a nanoimprint lithography process. The output power of these flip-chip (FC) DUV LEDs was measured and analyzed in a ray-tracing simulation using NPSSs: cones with diameters of 2.5 mu m (LED1), 400 (LED2) and 200 nm (LED3) as well as holes with diameters of 350 (LED4) and 750 nm (LED5). For comparison, a mirror for the c-plane FC DUV LEDs was introduced by coating Ni/Au and Al thin films. With the injection current at 350 mA, the output powers of the c-plane, LED1, LED2, LED3, LED4, and LED5 were 13.38, 14.68, 20.05, 16.79, 15.74, and 18.93 mW, respectively. The LED2 efficiency improved 49.9% compared with mirror LED and the result was consistent with ray-tracing simulation. (C) The Author(s) 2019. Published by ECS.
Deep-Ultraviolet Photodetectors Based on Epitaxial ZnGa(2)O(4 )Thin Films
(2018-09-19)
Tsai, Si-Han
;
Basu, Sarbani
;
Huang, Chiung-Yi
;
Hsu, Liang-Ching
;
Lin, Yan-Gu
A single-crystalline( )ZnGn(2)O(4) ( )epilayer was successfully grown on c-plane (0001) sapphire substrate by metal-organic chemical vapor deposition. This epilayer was used as a ternary oxide semiconductor for application in high-performance metal-semiconductor-metal photoconductive deep-ultraviolet (DUV) photodetectors (PDs). At a bias of 5V, the annealed ZnGn(2)O(4) PDs showed better performance with a considerably low dark current of 1 pA, a responsivity of 86.3 A/W, cut-off wavelength of 280 nm, and a high DUV-to-visible discrimination ratio of approximately 10(7) upon exposure to 230 nm DUV illumination than that of as-grown ZnGn(2)O(4 )PDs. The as-grown PDs presented a dark current of 0.5 mA, a responsivity of 2782 A/W at 230 nm, and a photo-to-dark current contrast ratio of approximately one order. The rise time of annealed PDs was 0.5 s, and the relatively quick decay time was 0.7 s. The present results demonstrate that annealing process can reduce the oxygen vacancy defects and be potentially applied in ZnGn(2)O(4) film-based DUV PD devices, which have been rarely reported in previous studies.
Deep-ultraviolet Schottky photodetectors with high deep-ultraviolet/visible rejection based on a ZnGa2O4 thin film
(2019-12-01)
Tsai, Si-Han
;
Shen, Yuan-Chu
;
Huang, Chiung-Yi
;
Horng, Ray-Hua
;
電子工程學系及電子研究所
A single-crystalline ZnGa2O4 epilayer was successfully grown on a c-plane (0001) sapphire substrate through metalorganic chemical vapor deposition. A metal-semiconductor-metal Schottky deep-ultraviolet (DUV) photodetector based on a ZnGa2O4 thin film was fabricated through a simple process of E-gun evaporation and thermal annealing. At a bias of 10 V, the ZnGa2O4 photodetectors exhibited excellent performance characteristics such as an extremely low dark current (0.86 pA), a responsivity of 0.46 A/W under 230-nm DUV, a high photo/dark current ratio (up to 4.68x10(4)), a sharp cutoff wavelength of approximately 270 nm, and short rise and fall times of 0.96 and 0.34 s. The photogenerated holes trapped in the Schottky barrier and the shrinking of the depletion region under DUV illumination enabled high DUV/visible rejection ratio (3-4 orders with a 20-V bias). Therefore, the Fowler-Nordheim field tunneling emission functioned as the main electron transport mechanism under DUV illumination and improved the photoelectric characteristics of the epilayer.
Development and Fabrication of AlGaInP-Based Flip-Chip Micro-LEDs
(2018-01-01)
Horng, Ray-Hua
;
Chien, Huan-Yu
;
Chen, Ken-Yen
;
Tseng, Wei-Yu
;
Tsai, Yu-Ting
The fabrication of AlGaInP-based flip-chip micro light-emitting-diodes (LED; emitting area: 4.5 mil x 5 mil) with horizontal electrodes is reported in this paper. The thickness of the epitaxial layer of the thin LED structure was reduced to 50% of that of the traditional thick LED, whereas carrier concentration in the n-type GaAs contact layer was increased to 5 x 10(18) cm(-3) to meet the Ohmic contact requirement. At a current injection of 5 mA, the thin LED exhibited a forward voltage, output power, and external quantum efficiency of 1.8 V, 1.9 mW, and 19%, respectively. The optoelectronic performance of the thin LED was as good as that of the traditional thick red LED. The technique proposed by this paper can be used to integrate AlGaInP-based LEDs with nitride LEDs for full-color display applications.
Effect of the Phosphor Permanent Substrate on the Angular CCT for White Thin-Film Flip-Chip Light-Emitting Diodes
(2016-10)
Tien, Ching-Ho
;
Ho, Kuo-Wei
;
Chien, Huan-Yu
;
Wuu, Dong-Sing
;
Horng, Ray-Hua
This paper developed a phosphor layer applied for thin-film flip-chip light-emitting diodes (TFFC-LEDs) to produce uniform phosphor-converted TFFC white LEDs (TFFC-WLEDs) by combination of laser liftoff, secondary transferring, and surface roughening process. The spin-coating method was used for phosphor layer fabrication onto a substrate to form the phosphor permanent substrate. The TFFC-LEDs were then bonded onto the permanent substrate. From the results, the blue TFFC GaN-based LED with roughened u-GaN surface on a glass substrate (TFRG-LED) demonstrated a 54.2% (at 350 mA) enhancement in light output power, compared with a blue flip-chip GaN-on-sapphire based LED. As the TFFC GaN/phosphor-/glass-based white LED with roughened u-GaN surface (TFRG-WLED) was operated at a forward-bias current of 350 mA, the enhancement of luminous flux was increased by 75.5%, compared with a TFFC GaN/phosphor template-/glass-based white LED. The angular correlated color temperature (CCT) deviation of a TFRG-WLED can be reduced to 1279 K in the range from -75 degrees to +75 degrees at 5000-6000 K application. The TFRG-WLED was fabricated on the glass substrate with the roughened u-GaN surface and the structure of phosphor layer closed to the u-GaN. These kinds of FRGB-WLED structure contribute to a better light extraction characteristic and a higher CCT stability.
Effect of Thermal Management on the Performance of VCSELs
(2020-09-01)
Pan, Po-Chou
;
Nag, Dhiman
;
Khan, Zuhaib
;
Chen, Ching-Jung
;
Shi, Jin-Wei
This study investigated the effect of thermal management on the performance of vertical-cavity surface-emitting lasers (VCSELs). It was found that the thickness of silicon substrate, which can serve as the submount for VCSEL packages, has a strong influence on the thermal dissipation of on-chip laser sources, and eventually impacts on their output characteristics. Moreover, the improvements in optical characteristics of the on-chip VCSELs were the best heat dissipation through thinning silicon substrates to 50-mu m thickness combined with electroplated Cu with 100-mu m thickness. In addition, this study also performed COMSOL simulations. The simulation results were consistent with experimental results.
Effect of Top-Region Area of Flat-Top Pyramid Patterned Sapphire Substrate on the Optoelectronic Performance of GaN-Based Light-Emitting Diodes
(2016-01-01)
Hsueh, Hsu-Hung
;
Ou, Sin-Liang
;
Peng, Yu-Che
;
Cheng, Chiao-Yang
;
Wuu, Dong-Sing
The flat-top pyramid patterned sapphire substrates (FTP-PSSs) have been prepared for the growth of GaN epilayers and the fabrication of lateral-type light-emitting diodes (LEDs) with an emission wavelength of approximately 470 nm. Three kinds of FTP-PSSs, which were denoted as FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C, respectively, were formed through the sequential wet etching processes. The diameters of circle areas on the top regions of these three FTP-PSSs were 1, 2, and 3 mu m, respectively. Based on the X-ray diffraction results, the full-width at half-maximum values of rocking curves at (002) plane for theGaN epilayers grown on conventional sapphire substrate (CSS), FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C were 412, 238, 346, and 357 arcsec, while these values at (102) plane were 593, 327, 352, and 372 arcsec, respectively. The SpeCLED-Ratro simulation results reveal that the LED prepared on FTP-PSS-A has the highest light extraction efficiency than that of the other devices. At an injection current of 350 mA, the output powers of LEDs fabricated on CSS, FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C were 157, 254, 241, and 233 mW, respectively. The results indicate that both the crystal quality of GaN epilayer and the light extraction of LED can be improved via the use of FTP-PSS, especially for the FTP-PSS-A.