Browsing by Author "Chiang, Chung-Hao"

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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.
Heteroepitaxial growth of InN on GaN intermediate layer by PA-MOMBE
(2011-07-01)
Lai, Fang-I
;
Kuo, Shou-Yi
;
Chen, Wei-Chun
;
Lin, Woei-Tyng
;
Wang, Wei-Lin
In this paper, high-quality wurtzite indium nitride was epi-grown on sapphire substrates by plasma-assisted metal-organic molecule beam epitaxy system (PA-MOMBE). Structural and electrical properties of the InN films were significantly improved by employing a GaN buffer layer. In addition, high-resolution X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), Hall Effect, Raman and photoluminescence spectroscopy were carried out to characterize the effect of the growth temperature on structural and optoelectronic properties. It was found that highly c-axis oriented InN epilayer can be obtained by optimizing growth conditions. TEM images reveal that the epitaxially grown InN/GaN interface is sharp, and the spacing of the InN(0 0 0 2) lattice plane is about 0.57 nm. Raman spectra also show a sharp peak at 491 cm(-1) attributed to the E(2)(high) mode of wurtzite InN. These results indicate that the improvement of InN material quality can be achieved using heteroepitaxy on GaN/sapphire templates. (C) 2011 Elsevier B.V. All rights reserved.