Browsing by Author "Shih, Ya-Hsuan"

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Design and Fabrication of the Reliable GaN Based Vertical-Cavity Surface-Emitting Laser via Tunnel Junction
(2019-04-01)
Shen, Chih-Chiang
;
Lu, Yun-Ting
;
Yeh, Yen-Wei
;
Chen, Cheng-Yuan
;
Chen, Yu-Tzu
In this study, we theoretically designed and experimentally fabricated an InGaN vertical-cavity surface-emitting laser (VCSEL) with a tunnel junction (TJ) structure. From numerical simulation results, the optical loss of the device can be reduced by a TJ structure. Additionally, the leakage current of the VCSEL with TJ structure was much smaller than that of the VCSEL with an Indium-Tin-Oxide (ITO) layer. We have been demonstrated that laser output performance is improved by using the TJ structure when compared to the typical VCSEL structure of the ITO layer. The output power obtained at 2.1 mW was enhanced by a factor of 3.5 by the successful reduction of threshold current density (J(th)) from 12 to 8.5 kA/cm(2), and the enlarged slope efficiency was due to less absorption in VCSEL with a TJ structure. Finally, the samples passed the high temperature (70 degrees C) and high operation current (1.5 x J(th)) test for over 500 h.
Simulation and Experimental Study on Barrier Thickness of Superlattice Electron Blocking Layer in Near-Ultraviolet Light-Emitting Diodes
(2016-08-01)
Kuo, Yen-Kuang
;
Chen, Fang-Ming
;
Lin, Bing-Cheng
;
Chang, Jih-Yuan
;
Shih, Ya-Hsuan
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.