Browsing by Author "Chang, Jih-Yuan"

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Numerical analysis on the effect of electron blocking layer in 365-nm ultraviolet light-emitting diodes
(2015-01-01)
Chen, Fang-Ming
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Chang, Jih-Yuan
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Kuo, Yen-Kuang
;
Lin, Bing-Cheng
;
Kuo, Hao-Chung
For 365-nm ultraviolet light-emitting diodes (UV LEDs), an electron blocking layer (EBL) is usually utilized to mitigate electron overflow. However, using EBL might obstruct holes from injecting into the active region. Moreover, the large polarization field in conventional EBL might also pull down the effective barrier height for electrons, and thus the electrons could easily overflow to the p-side region. To solve the above drawbacks, in this study, the Al content and p-doping concentration of the EBL in typical 365-nm UV LEDs are investigated systematically. Specifically, designs of AlGaN/GaN superlattice EBL and Al-content-graded EBL are explored in detail.
Numerical Study of (0001) Face GaN/InGaN p-i-n Solar Cell With Compositional Grading Configuration
(2012-06-15)
Kuo, Yen-Kuang
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Lin, Bing-Cheng
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Chang, Jih-Yuan
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Chen, Fang-Ming
;
Kuo, Hao-Chung
The advantages of a (0001) face GaN/InGaN p-i-n solar cell with compositional grading configuration between i-InGaN/p-GaN layers are studied numerically. With the use of the grading layer, the conversion efficiency is markedly promoted due to the reduction of potential barrier height for holes and due to the decrease of polarization. Optimized conversion efficiency is obtained when the thickness of the grading layer increases to a critical value. This critical thickness is strongly influenced by the polarization charges and doping concentration of the grading layer. When the density of the polarization charges is high or the doping concentration is low, a thick grading layer is required to achieve high efficiency.
Simulation and Experimental Study on Barrier Thickness of Superlattice Electron Blocking Layer in Near-Ultraviolet Light-Emitting Diodes
(2016-08-01)
Kuo, Yen-Kuang
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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.