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Open AccessArticle

Effect of Strains and V-Shaped Pit Structures on the Performance of GaN-Based Light-Emitting Diodes

1
Department of Photonics, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
2
Epistar Corporation, Hsinchu 300, Taiwan
*
Author to whom correspondence should be addressed.
Crystals 2020, 10(4), 311; https://doi.org/10.3390/cryst10040311
Received: 7 March 2020 / Revised: 10 April 2020 / Accepted: 14 April 2020 / Published: 17 April 2020
(This article belongs to the Special Issue GaN-Based Optoelectronic Materials and Light Emitting Devices)
Strains and V-shaped pits are essential factors for determining the efficiency of GaN-based light-emitting diodes (LEDs). In this study, we systematically analyzed GaN LED structures on patterned sapphire substrates (PSSs) with two types of growth temperature employed for prestrained layers and three different thickness of n-type GaN layers by using cathodoluminescence (CL), microphotoluminescence (PL), and depth-resolved confocal Raman spectroscopy. The results indicated that V-pits formation situation can be analyzed using CL. From the emission peak intensity ratio of prestrained layers and multiple quantum wells (MQWs) in the CL spectrum, information regarding strain relaxation between prestrained layers and MQWs was determined. Furthermore, micro-PL and depth-resolved confocal Raman spectroscopy were employed to validate the results obtained from CL measurements. The growth conditions of prestrained layers played a dominant role in the determination of LED performance. The benefit of the thick layer of n-GaN was the strain reduction, which was counteracted by an increase in light absorption in thick n-type doped layers. Consequently, the most satisfactory LED performance was observed in a structure with relatively lower growth temperature of prestrained layers that exhibited larger V-pits, leading to higher strain relaxation and thinner n-type GaN layers, which prevent light absorption caused by n-type GaN layers. View Full-Text
Keywords: GaN; light emitting diodes; V-shaped pits; strain GaN; light emitting diodes; V-shaped pits; strain
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MDPI and ACS Style

Chen, S.-W.; Chang, C.-J.; Lu, T.-C. Effect of Strains and V-Shaped Pit Structures on the Performance of GaN-Based Light-Emitting Diodes. Crystals 2020, 10, 311.

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