Effect of Top-Region Area of Flat-Top Pyramid Patterned Sapphire Substrate on the Optoelectronic Performance of GaN-Based Light-Emitting Diodes

Hsu-Hung Hsueh,Dong-Sing Wuu,Sin-Liang Ou,Chiao-Yang Cheng,Ray-Hua Horng,Yu-Che Peng

doi:10.1155/2016/2701028

Hsu-Hung Hsueh, Dong-Sing Wuu + Show 4 more

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https://doi.org/10.1155/2016/2701028

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Abstract

The flat-top pyramid patterned sapphire substrates (FTP-PSSs) have been prepared for the growth of GaN epilayers and the fabrication of lateral-type light-emitting diodes (LEDs) with an emission wavelength of approximately 470 nm. Three kinds of FTP-PSSs, which were denoted as FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C, respectively, were formed through the sequential wet etching processes. The diameters of circle areas on the top regions of these three FTP-PSSs were 1, 2, and 3 μm, respectively. Based on the X-ray diffraction results, the full-width at half-maximum values of rocking curves at (002) plane for the GaN epilayers grown on conventional sapphire substrate (CSS), FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C were 412, 238, 346, and 357 arcsec, while these values at (102) plane were 593, 327, 352, and 372 arcsec, respectively. The SpeCLED-Ratro simulation results reveal that the LED prepared on FTP-PSS-A has the highest light extraction efficiency than that of the other devices. At an injection current of 350 mA, the output powers of LEDs fabricated on CSS, FTP-PSS-A, FTP-PSS-B, and FTP-PSS-C were 157, 254, 241, and 233 mW, respectively. The results indicate that both the crystal quality of GaN epilayer and the light extraction of LED can be improved via the use of FTP-PSS, especially for the FTP-PSS-A.

Highlights

GaN-based materials have received a lot of attention for many optoelectronic applications consisting of lightemitting diodes (LEDs), laser diodes, and high-power devices [1,2,3]
Three various FTP-patterned sapphire substrate (PSS), that were denoted as flat-top pyramidal PSS (FTP-PSS)-A, FTP-PSS-B, and FTP-PSS-C, respectively, were formed via the sequential wet etching processes
This indicates that the FTP-PSSC has the largest c-plane area of flat-top region, while the FTPPSS-A possesses the smallest one among these three samples

Summary

Introduction

GaN-based materials have received a lot of attention for many optoelectronic applications consisting of lightemitting diodes (LEDs), laser diodes, and high-power devices [1,2,3]. The formation of mask could induce the impurity contamination in the subsequent epilayers To overcome these mask-related drawbacks, the mask-free patterned sapphire substrate (PSS) technology has been proposed and becomes very promising for the growth of high-quality GaN epilayer [7,8,9,10]. The InGaN/GaN film with high crystal quality can be achieved using metalorganic chemical vapor deposition (MOCVD) on the flat-top pyramidal PSS (FTP-PSS) [8,9,10]. These researches confirm that the FTPPSSs are helpful to enhance the performance of LEDs. the influence of pattern size of the FTP-PSS on the device characteristics is seldom studied. The effect of the flat-top region area of FTP-PSS on the device performance was investigated

Experimental

Results and Discussion

Conclusion