Browsing by Author "Tseng, Ming-Chun"

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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%.
Enhanced light extraction in wafer-bonded p-side-up thin-film AlGaInP light emitting diodes via zinc oxide nanorods
(2016-10-01)
Tseng, Ming-Chun
;
Wuu, Dong-Sing
;
Chen, Chi-Lu
;
Lee, Hsin-Ying
;
Lin, Yu-Chang
ZnO nanorods grown via hydrothermal method on the aluminum-doped zinc oxide (AZO) thin film were used to fabricate high-brightness p-side-up thin-film AlGaInP light-emitting diodes (LEDs). The AZO thin film was not only used as current spreading layers but also as a seed layer of ZnO nanorods. The AZO thin film was prepared using atomic layer deposition. The ZnO nanorods improved light extraction, thus increasing the light output power of the LEDs. The output powers of LEDs with optimum ZnO nanorod structures were increased by 32% at an injection current of 700 mA, as compared with that of an LED with AZO thin film. The emission wavelength shifts of LEDs with an AZO thin film and optimum ZnO nanorod structure were 18 and 11 nm, respectively, when the injection current was increased from 20 to 1000 mA. The ZnO nanorods not only provide more light extraction but also keep the thermal stability of the LED device without any degradation. The results are promising for the developed high brightness AlGaInP LED applications with low fabrication cost through ZnO nanorods grown by hydrothermal method to enhance the light extraction efficiency. (C) 2016 Optical Society of America
Ohmic contact behavior of aluminum-doped zinc oxide with carbondoped p-GaP epilayer for AlGaInP LEDs applications
(2017-07-01)
Tseng, Ming-Chun
;
Wuu, Dong-Sing
;
Chen, Chi-Lu
;
Lee, Hsin-Ying
;
Horng, Ray-Hua
Aluminum-doped zinc oxide (AZO) thin films used for ohmic contact layers on carbon-doped GaP window layers (p-GaP:C) of AlGaInP light-emitting diodes were fabricated and characterized. AZO thin films with different Zn:Al cycle ratios (15:1, 20:1, and 25:1) were deposited on p-GaP:C window layers through atomic layer deposition. The contact characteristics of the AZO thin films on p-GaP:C were considerably changed from Schottky contact to ohmic contact after rapid thermal annealing (RTA) at 350 degrees C for 1 min. The most favorable specific contact resistance of AZO/p-GaP:C was evaluated using a circular transmission line model as 6.3 x 10(-3) Omega/cm(2). Angle-resolved X-ray photoelectron spectroscopy was employed to understand the ohmic contact behavior of AZO/p-GaP:C. After RTA, Zn atoms in the AZO thin films notably diffused into the p-GaP:C layers and Ga atoms diffused out of the p-GaP:C layer. Therefore, the Ga vacancies were occupied by Zn atoms, which increased the doping concentration in the near-surface region of p-GaP:C and reduced the depletion region width of the semiconductor region. Thus, numerous carriers were able to tunnel through the reduced Schottky barrier and those carriers produced the ohmic contact behavior between the AZO and p-GaP:C. (C) 2017 Elsevier B. V. All rights reserved.
Performance comparison of p-side-up thin-film AlGaInP light emitting diodes with aluminum-doped zinc oxide and indium tin oxide transparent conductive layers
(2016-04-01)
Tseng, Ming-Chun
;
Wuu, Dong-Sing
;
Chen, Chi-Lu
;
Lee, Hsin-Ying
;
Lin, Yu-Chang
Transparent conductive layers (TCLs) deposited on a GaP window layer were used to fabricate high-brightness p-side-up thin-film AlGaInP light-emitting diodes (LEDs) by the twice wafer-transfer technique. Indium tin oxide (ITO) and aluminum-doped zinc oxide (AZO) were used as TCLs for comparison. The TCLs improved droop of external quantum efficiencies (EQE) of LEDs and junction temperature, which result in increasing the light output power and thermal stability of the LEDs. The droop efficiency of Ref-LED, ITO-LED and AZO-LED were 64%, 27% and 15%, respectively. The junction temperature of ITO-LED and AZO-LED reduced to 49.3 and 39.6 degrees C at an injection current of 700 mA compared with that (80.8 degrees C) of Ref-LED. The LEDs with AZO layers exhibited the most excellent LED performance. The emission wavelength shifts of LEDs without a TCL, with an ITO layer, and with an AZO layer were 17, 8, and 3 nm, respectively, when the injection current was increased from 20 to 1000 mA. The above results are promising for the development of AZO thin films to replace ITO thin films for AlGaInP LED applications. (C) 2016 Optical Society of America
Performance Comparisons of Light-Emitting Thyristors with and without Indium Tin Oxide Transparent Conductive Layers
(2018-04-21)
Chen, Ching-Ho
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Tseng, Ming-Chun
;
Chen, Yu-Jie
;
Wuu, Dong-Sing
;
Horng, Ray-Hua
Indium tin oxide (ITO) deposited on different contact layers are studied to be used as transparent electrodes on light-emitting thyristors (LETs). The performance of LETs with either ITO or a metal electrode is compared. It is found that the ITO could be used as an ohmic contact layer, because the ITO layer was deposited on the contact layer with heavy dopant concentration. Moreover, the thermal annealing at 400 degrees C is necessary. The S-shaped current-voltage characteristic of LETs with either metal or ITO electrodes is compared. The LETs with an ITO thin film exhibit excellent performance. The light output power and thermal stability of the LETs with the ITO layer are higher than those of the LETs with the metal electrode. The light-extraction efficiency of the ITO-LET is 24% higher than that of the metal-LET. The surface temperature of the ITO-LET is 9.57 degrees C lower than that of the metal-LET. The ITO electrode on the LET chip significantly improved the light intensity distribution properties as compared with the metal electrode on the LET chip. The above results are promising for the development of ITO thin films to enhance the performance of LET applications.
Performance of p-side-up thin-film AlGaInP light-emitting diodes with textured composite aluminum-doped zinc oxide transparent conductive layers
(2017-06-25)
Tseng, Ming-Chun
;
Wuu, Dong-Sing
;
Chen, Chi-Lu
;
Lee, Hsin-Ying
;
Lin, Yu-Chang
Composite transparent conductive layers (TCLs) were deposited on the GaP window layer of p-side-up thin-film AlGaInP light-emitting diodes (LEDs) in order to enhance their light-extraction efficiency. The composite TCLs were fabricated from aluminum-doped zinc oxide (AZO) layers grown through atomic-layer deposition and pulsed-laser deposition. The results showed that wet-etching of composite AZO thin films improved the light extraction efficiency of the corresponding LED devices. The droop efficiencies of LEDs with flat AZO thin films, composite AZO thin films, and optimum textured composite AZO thin films were 29%, 30%, and 22%, respectively. LEDs with textured composite AZO layers exhibited favorable optoelectronic performance. When the injection current was increased from 20 to 1000 mA, the emission wavelengths of LEDs with flat AZO thin films, composite AZO thin films, and optimum textured composite AZO thin films shifted by 3, 5, and 3 nm, respectively. The optimum textured composite AZO thin film can not only improve LED performance but also effectively substitute flat TCLs in AlGaInP LED applications. (C) 2016 Elsevier B.V. All rights reserved.
Surface Treatments on the Characteristics of Metal-Oxide Semiconductor Capacitors
(2019-01-01)
Horng, Ray-Hua
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Tseng, Ming-Chun
;
Wuu, Dong-Sing
;
交大名義發表
;
電子工程學系及電子研究所
The properties of metal-oxide semiconductor (MOS) capacitors with different chemical treatments have been examined in this study. A MOS capacitor consists of an Al2O3/n-GaN/AlN buffer/Si substrate. Four chemical treatments, containing organic solvents, oxygen plasma and BCl3 plasma, dilute acidic and alkali solvents, and hydrofluoric acid, were used to reduce the metal ions, native oxides, and organic contaminants. The n-GaN surface was treated with these chemical treatments before Al2O3 was grown on the treated n-GaN surface to reduce the interface state trap density (D-it). The value of D-it was calculated using the capacitance-voltage curve at 1 MHz. The D-it of a u-GaN surface was modified using various solutions, which further influenced the contact properties of GaN.
Zinc oxide-based current spreading layer behavior on the performance of P-side-up thin-film red light emitting diodes
(2018-02-28)
Tseng, Ming-Chun
;
Wuu, Dong-Sing
;
Chen, Chi-Lu
;
Lee, Hsin-Ying
;
Horng, Ray-Hua
Transparent conductive layers deposited on a GaP window layer were used to fabricate high-brightness p-side-up thin-film AlGaInP light emitting diodes (LEDs). Zinc oxide (ZnO) and aluminum-doped zinc oxide (ZAO) with an Zn:Al cycle ratio of 20:1 were grown by atomic layer deposition for comparison. The ZAO thin films reduced the droop in the external quantum efficiencies of the LEDs as well as the junction temperature, which result in increases in the light output power and thermal stability of the LEDs. The efficiency droops of the LEDs with the ZnO and ZAO thin films were 41% and 15%, respectively. The junction temperature of the LED with the ZAO thin film can be reduced to 39.6 degrees C at an injection current of 700 mA, which is lower than that of the LED with the ZnO thin film (58.1 degrees C). The above results are promising for the development of ZAO thin films for applications in AlGaInP LEDs. (C) 2017 Elsevier B.V. All rights reserved.