Browsing by Author "Lin, Ray-Ming"

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Efficiency improvement of GaN-based ultraviolet light-emitting diodes with reactive plasma deposited AlN nucleation layer on patterned sapphire substrate
(2014-09-16)
Lee, Chia-Yu
;
Tzou, An-Jye
;
Lin, Bing-Cheng
;
Lan, Yu-Pin
;
Chiu, Ching-Hsueh
The flip chip ultraviolet light-emitting diodes (FC UV-LEDs) with a wavelength of 365 nm are developed with the ex situ reactive plasma deposited (RPD) AlN nucleation layer on patterned sapphire substrate (PSS) by an atmospheric pressure metal-organic chemical vapor deposition (AP MOCVD). The ex situ RPD AlN nucleation layer can significantly reduce dislocation density and thus improve the crystal quality of the GaN epitaxial layers. Utilizing high-resolution X-ray diffraction, the full width at half maximum of the rocking curve shows that the crystalline quality of the epitaxial layer with the (RPD) AlN nucleation layer is better than that with the low-temperature GaN (LT-GaN) nucleation layer. The threading dislocation density (TDD) is estimated by transmission electron microscopy (TEM), which shows the reduction from 6.8 x 10(7) cm(-2) to 2.6 x 10(7) cm(-2). Furthermore, the light output power (LOP) of the LEDs with the RPD AlN nucleation layer has been improved up to 30 % at a forward current of 350 mA compared to that of the LEDs grown on PSS with conventional LT-GaN nucleation layer.
Enhanced Extraction and Efficiency of Blue Light-Emitting Diodes Prepared Using Two-Step-Etched Patterned Sapphire Substrates
(2009)
Lin, Ray-Ming
;
Lu, Yuan-Chieh
;
Yu, Sheng-Fu
;
Wu, YewChung Sermon
;
Chiang, Chung-Hao
Using a hot acid wet etching method, we have fabricated two types of patterned sapphire substrates: A pyramidal patterned sapphire substrate (PPSS) and a flat-top patterned sapphire substrate (FTPSS). After placing these samples into an atmospheric pressure metallorganic chemical vapor deposition system, we deposited standard InGaN light-emitting diode (LED) structures onto their surfaces. The crystal quality of these two surfaces was enhanced, as evidenced using X-ray diffraction (the full width at half-maximum decreased from 406.8 arcsec for the conventional sapphire to 356.4 and 349.2 arcsec for the PPSS and FTPSS samples, respectively). The output power of InGaN-based blue LEDs incorporating the PPSS and FTPSS improved to 17.9 and 18.7%, respectively, at 20 mA. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3231502] All rights reserved.
Influence of patterned sapphire substrates with different symmetry on the light output power of InGaN-based LEDs
(2014-11-03)
You, Yao-Hong
;
Su, Vin-Cent
;
Ho, Ti-En
;
Lin, Bo-Wen
;
Lee, Ming-Lun
This paper aims to investigate the light output power (LOP) of InGaN-based light-emitting diodes (LEDs) grown on patterned sapphire substrates (PSSs) with different symmetry. The GaN epitaxial layers grown on the hexagonal lattice arrangement PSS (HLAPSS) have a lower compressive strain than the ones grown on the square lattice arrangement PSS (SLAPSS). The quantum-confined Stark effect (QCSE) is also affected by the residual compressive strain. Based on the experimentally measured data and the ray tracing simulation results, the InGaN-based LED with the HLAPSS has a higher LOP than the one with the SLAPSS due to the weaker QCSE within multiple-quantum wells (MQWs).
Suppression of "volcano" morphology and parasitic defect luminescence in AlGaN-based deep-UV light-emitting diode epitaxy
(2019-06-01)
Huang, Chia-Yen
;
Liu, Tsung-Yen
;
Huang, Shih-Ming
;
Chang, Kai-Hsiang
;
Tai, Tsu-Ying
In this study we overcame several critical growth issues related to epitaxy in AlGaN deep-ultraviolet lightemitting diodes. Irregular-shaped pits with dislocation clusters were observed in micron-thick layers of AlGaN on AlN. The strain-induced morphology and defects were suppressed after the insertion of superlattice transition layers between the AlGaN and AlN layers. The defect luminescence in the active region was governed by radiative recombination through the oxygen shallow donors and deep acceptors related to III-vacancies. After optimization of the growth conditions and a decrease in growth interruption, the intensity of the parasitic blueband emission was suppressed by up to 95%. Energy dispersive spectroscopy suggests that the desorption of gallium from the surface is the major source of the III-vacancies.
The Analysis of Nano-Patterned Sapphire Substrates-Induced Compressive Strain to Enhance Quantum-Confined Stark Effect of InGaN-Based Light-Emitting Diodes
(2013-01-01)
Chen, Po-Hsun
;
Su, Vincent
;
You, Yao-Hong
;
Lee, Ming-Lun
;
Hsieh, Cheng-Ju
This paper demonstrates that the quantum-confined stark effect of InGaN-based light-emitting diodes can be enhanced by the means of using the hexagonal nano-post patterned sapphire substrates based on the increase of the post-duty cycle.
The origin and mitigation of volcano-like morphologies in micron-thick AlGaN/AlN heteroepitaxy
(2017-08-14)
Huang, Chia-Yen
;
Chang, Kai-Shiang
;
Huang, Cheng-Yao
;
Lin, Yun-Hsiang
;
Peng, Wei-Chih
We investigated the origin of morphological instability in 2 mu m thick Al0.6Ga0.4N/AlN heteroepitaxy. The primary morphology was driven by the residual epitaxial strain, forming hill-like morphologies via surface diffusion. The secondary morphology was driven by the interaction between the primary morphology and dislocation clusters in the epitaxial layers. The difference in the local growth rate yields volcano-like morphologies centering on deep pits. Insertion of multi-stack superlattice transition layers between AlGaN and GaN effectively suppressed the secondary morphologies by simultaneously pre-relaxing the template and filtering treading dislocations. Published by AIP Publishing.
Using BCl3-Based Plasma to Modify Wet-Etching Pattern Sapphire Substrate for Improving the Growth of GaN-Based LEDs
(2013-02-15)
Lin, Bo-Wen
;
Niu, Chen-Yi
;
Hsieh, Cheng-Yu
;
Wang, Bau-Ming
;
Hsu, Wen-Ching
Wet-etching pattern sapphire substrates (PSS) have been used to grow GaN-based light-emitting diodes (LEDs). However, after wet etching, several sidewall facets are exposed on the patterns of PSS. These sidewall facets would grow zincblende GaN and form irregular voids. In this letter, BCl3-based plasma is used to solve this problem and improve the performance of GaN-based LEDs.