Ya‐Hsuan Shih

National Cheng Kung University

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Yen‐Kuang Kuo

National Changhua University of Education

Jih‐Yuan Chang

National Changhua University of Education

Fang‐Ming Chen

Zhejiang Chinese Medical University

Man-Fang Huang

National Changhua University of Education

Jinn‐Kong Sheu

National Cheng Kung University

Bo-Ting Liou

Hsiuping University of Science and Technology

Ming-Lun Lee

Southern Taiwan University of Science and Technology

Hao‐Chung Kuo

National Yang Ming Chiao Tung University

Sung‐Wen Huang Chen

National Yang Ming Chiao Tung University

Yen‐Lung Huang

National Changhua University of Education

Cooperative Institutions

National Changhua University of Education

National Yang Ming Chiao Tung University

National Cheng Kung University

National Central University

National Taiwan University

National Tsing Hua University

University of Southern California

Industrial Technology Research Institute

Southern Taiwan University of Science and Technology

University of California, Santa Barbara

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Achievement of 110-nm-Wide Spectral Width in Monolithic Tunnel-Junction Light-Emitting Diode

IEEE Journal of Quantum Electronics (2021)

Man-Fang Huang Ya‐Hsuan Shih Jih‐Yuan Chang Yen‐Lung Huang Jinn‐Kong Sheu

Characterization and structural design on monolithic stacked InGaN light-emitting diode (LED) are investigated numerically in an attempt to pursue multicolor light emission and wide spectral width. Crucial physical properties such as the energy band configurations, carrier distributions, and interband transitions are analyzed in detail, which are also utilized as an aid to justify the desired characteristics of the LED structures under study. The compositions of multi-quantum wells, as well as the thicknesses of quantum barriers in each unit stacked LED are appropriately adjusted to simplify the tandem LED structure and optimize the overall emission spectra. Upon optimization, a monolithic tunnel-junction LED with an emission spectral width of approximately 110 nm, full width at half maximum, is demonstrated with only three unit stacked LEDs and two tunnel junctions.

Spectral width

Tunnel junction

Tandem

Tunnel diode

10.1109/jqe.2021.3079419

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Citations (1)

III-Nitride Based Cyan Light-Emitting Diodes with GHz Bandwidth for High-Speed Visible Light Communication

IEEE Electron Device Letters (2016)

Jin‐Wei Shi Kai-Lun Chi Jhih-Min Wun John E. Bowers Ya‐Hsuan Shih

A large reduction (from 17 to 5 nm) is made in the thickness of the barrier layers in the multiple-quantum-well region of III-nitride-based cyan light-emitting diodes (LEDs) grown on patterned sapphire substrates. This is shown to lead to a simultaneous improvement in the modulation speed, differential quantum efficiency, and maximum output power of the LEDs under both room temperature and 110 °C operation. With our novel device structure, we achieve a moderate output power (1.7 mW) with a record high 3-dB electrical-to-optical (E-O) bandwidth (1 GHz). The over twofold enhancement in the E-O bandwidth (~1 versus ~0.5 GHz) compared with that previously reported visible LEDs can be attributed to the more uniform distribution of injected carriers within the MQW region and the aggressive downscaling of the thickness of the total active layer, which leads to a shortening of the spontaneous recombination time.

Cyan

Quantum Efficiency

10.1109/led.2016.2573265

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Citations (43)

Design of GaN-Based Multicolor Tunnel-Junction Light-Emitting Diodes

IEEE Transactions on Electron Devices (2017)

Ya‐Hsuan Shih Jih‐Yuan Chang Yen‐Kuang Kuo Fang‐Ming Chen Man-Fang Huang

The design of monolithic multicolor tunnel-junction (TJ) light-emitting diodes (LEDs) are investigated numerically. This paper primarily aims to design and study monolithic TJ LED devices that possess high luminous efficiency and wide color gamut using a simple fabrication process. First, the characteristics of green and blue single LEDs are explored. Nonuniform carrier distribution inside quantum wells (QWs), which is due to the deep QWs and severe polarization effect, is observed for both single LEDs under study. Based on structural analysis of the single LEDs, streamline dual-color and broadband TJ LED structures, in which the blue unit LED has two pairs of 3-nm-thick QWs and the green unit LED has 3-nm-thick single QW, are designed and investigated. Specifically, monolithic dual-color blue/green (459/530 nm) TJ LED is proposed and analyzed using effective n ⁺ -GaN/i-In _0.2 Ga _0.8 N/p ⁺ -GaN TJ. Furthermore, broadband TJ LED with simulated full width at half maximum of around 100 nm is achieved.

10.1109/ted.2017.2773660

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Design and Optimization of Electron-Blocking Layer in Deep Ultraviolet Light-Emitting Diodes

IEEE Journal of Quantum Electronics (2019)

Yen‐Kuang Kuo Fang‐Ming Chen Jih‐Yuan Chang Man-Fang Huang Bo-Ting Liou

Optical and electrical performance and the relevant physical properties of deep ultraviolet (DUV) AlGaN-based light-emitting diodes (LEDs) are numerically investigated. The influence of bulk AlGaN electron-blocking layer (EBL) with various Al compositions and Mg-doping concentrations on the output performance of DUV LEDs is systemically explored. Simulation results show that the DUV LED with bulk Al _0.85 Ga _0.15 N EBL with a relatively low Mg-doping concentration of 2×10 ¹⁹ cm ^-3 may have high wall-plug efficiency. The LED structure with Al _0.55 Ga _0.45 N/Al _0.75 Ga _0.25 N superlattice (SL) EBL is proposed in this study, which is shown to have high wall-plug efficiency similar to the LED with bulk Al _0.85 Ga _0.15 N EBL while the Al composition of AlGaN EBL can be effectively reduced. The proposed LED structure with SL EBL provides a practical way to fabricate high-crystalline-quality and high-efficiency DUV LEDs.

Ultraviolet

10.1109/jqe.2019.2957575

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Citations (22)

Numerical Study of the Effects of Hetero-Interfaces, Polarization Charges, and Step-Graded Interlayers on the Photovoltaic Properties of (0001) Face GaN/InGaN p-i-n Solar Cell

IEEE Journal of Quantum Electronics (2011)

Yen‐Kuang Kuo Jih‐Yuan Chang Ya‐Hsuan Shih

The photovoltaic properties of (0001) face GaN/InGaN p-i-n solar cell are studied numerically. The simulation results show that the detrimental effects of hetero-interfaces and polarization charges will seriously degrade the solar cell performance, especially when the indium composition is high. If these effects are not eliminated or diminished, the photovoltaic properties would not be good enough for practical applications even if a high-quality crystal could be obtained. For this purpose, the step-graded interlayers between the GaN-InGaN interfaces are introduced in order to overcome both aforementioned critical effects. The impacts of the thickness and p-type doping concentration of the step-graded interlayers are also investigated in detail.

10.1109/jqe.2011.2181972

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Citations (31)

Efficient Carrier Confinement in Deep-Ultraviolet Light-Emitting Diodes With Composition-Graded Configuration

IEEE Transactions on Electron Devices (2017)

Jih‐Yuan Chang Hui-Tzu Chang Ya‐Hsuan Shih Fang‐Ming Chen Man-Fang Huang

Characteristics of deep-ultraviolet (DUV) light-emitting diodes (LEDs) are investigated. DUV LEDs possess severe electron current leakage due to insufficient carrier confinement of the active region. Simply increasing the Al composition of quantum barriers (QBs) or electron-blocking layer (EBL) to enlarge the relevant potential barrier height would arise unexpected detrimental effects, such as extra polarization effect or more obstruction for hole injection. In this paper, band-engineered composition-graded QBs and EBL are proposed to resolve this issue. Simulation results show that, with appropriate designs, the leakage current of DUV LEDs could be effectively diminished with just slight side effects.

Ultraviolet

Leakage (economics)

Wide-bandgap semiconductor

10.1109/ted.2017.2761404

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Citations (29)

Design of Hole-Blocking and Electron-Blocking Layers in Al_xGa_1-xN-Based UV Light-Emitting Diodes

IEEE Transactions on Electron Devices (2016)

Ya‐Hsuan Shih Jih‐Yuan Chang Jinn‐Kong Sheu Yen‐Kuang Kuo Fang‐Ming Chen

The band-engineered structure design for electron-blocking layer (EBL) and hole-blocking layer (HBL) in Al _x Ga _1–x N-based ultraviolet light-emitting diodes (UV LEDs) is performed and analyzed theoretically. Simulation results show that the severe polarization effect is efficiently mitigated and the downward-bended band profile of the EBL is improved when the EBL is designed with a graded-composition and multiquantum barrier (GMQB) structure. As a result, the capabilities of both electron confinement and hole injection, and also the light output power are promoted. On the contrary, for the HBL, the design of composition graded and/or multiquantum barrier structures reduces the effective potential barrier height for holes in the valence band and, consequently, causes a considerable hole overflow. The UV LED, thus, exhibits superior optical performance when the LED structure is simultaneously designed with a GMQB EBL and a bulk HBL.

Blocking (statistics)

Ultraviolet

Electron hole

10.1109/ted.2016.2520998

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Citations (36)

High-Efficiency Deep-Ultraviolet Light-Emitting Diodes With Efficient Carrier Confinement and High Light Extraction

IEEE Transactions on Electron Devices (2019)

Jih‐Yuan Chang Bo-Ting Liou Man-Fang Huang Ya‐Hsuan Shih Fang‐Ming Chen

In deep-ultraviolet (DUV) light-emitting diodes (LEDs), it is difficult to obtain both efficient carrier confinement and high light extraction, which are quite sensitive to optical polarization and other physical parameters. In this paper, characteristics of DUV LEDs with various n-AlGaN layers and quantum barriers (QBs), and various widths of quantum wells (QWs) are investigated. Specifically, the capability of carrier confinement and properties of optical polarization are analyzed in detail. The simulation results show that LED structure with Al _0.64 Ga _0.36 N QBs, n-Al _0.7 Ga _0.3 N layer, and 4-nm-thick QWs, which has a peak emission wavelength of 284.5 nm at 60 mA, exhibits high internal quantum efficiency of 25% and high degree of optical polarization of 0.874.

Ultraviolet

Quantum Efficiency

10.1109/ted.2018.2887074

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Citations (20)

Simulation and Experimental Study on Barrier Thickness of Superlattice Electron Blocking Layer in Near-Ultraviolet Light-Emitting Diodes

IEEE Journal of Quantum Electronics (2016)

Yen‐Kuang Kuo Fang‐Ming Chen Bing-Cheng Lin Jih‐Yuan Chang Ya‐Hsuan Shih

The optical performance and relevant physical properties of near-ultraviolet (NUV) GaN-based light-emitting diodes (LEDs) are investigated. Specifically, the influence of traditional AlGaN bulk electron blocking layer (EBL) and AlGaN/GaN superlattice (SL) EBL with various thicknesses of AlGaN layers on NUV LEDs is explored. It is indicated from the band diagrams, electrostatic field profile, electron reflecting and hole transmitting spectra, and carrier concentrations profile that the use of a thin AlGaN layer of AlGaN/GaN SL EBL is beneficial to the electron confinement and hole injection in the active region, which results in the high internal quantum efficiency and low efficiency droop at high injection current. Moreover, the experimental results show that replacing the traditional AlGaN bulk EBL with the AlGaN/GaN SL EBL can markedly improve the optical performance. When compared with the NUV LED with traditional AlGaN bulk EBL, the output power of the NUV LED with the proposed AlGaN/GaN SL EBL increases from 13.5 to 48.7 mW at 100 mA.

Ultraviolet

Quantum Efficiency

Wide-bandgap semiconductor

10.1109/jqe.2016.2587100

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Citations (29)

Auger Recombination in Monolithic Dual-Wavelength InGaN Light-Emitting Diodes

Journal of Display Technology (2016)

Yen‐Kuang Kuo Tsun-Hsin Wang Yi-An Chang Jih‐Yuan Chang Fang‐Ming Chen

Auger recombination of dual-wavelength emission in monolithic InGaN light-emitting diodes (LEDs) is numerically investigated. Simulation results show that effective suppression of Auger recombination plays an important role toward the realization of dual-wavelength emission in InGaN LEDs. With appropriate design, the carriers in active region can be spatially and spectrally balanced and thereby effective dual-wavelength emission can be achieved.

Auger effect

10.1109/jdt.2016.2594044

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Citations (5)