Utilizing Two Dimensional Photonic Crystals in Different Arrangement to Investigate the Correlation between the Air Duty Cycle and the Light Extraction Enhancement of InGaN-Based Light-Emitting Diodes
Date Issued
2014
Date
2014
Author(s)
Lee, Ming-Lun
Abstract
This doctoral dissertation utilizes two dimensional (2-D) photonic crystals (PhCs) in different arrangement to investigate the correlation between the air duty cycle (ADC) and the light extraction enhancement (LEE) of InGaN-Based light-emitting diodes (LEDs). The 2-D periodical nano PhCs were achieved by using e-beam lithography and the dry etching technique.
Implementing 2-D PhCs to improve the light extraction efficiency of InGaN-based LEDs has been pursued widely, due to the significant improvement of the LEE while using PhCs. Thus, in implementing 2-D PhCs, there are three main parameters should be taken into consideration carefully. They are lattice constant, depth, and ADC. Until now, there have been few literature reports on investigating the correlation between the ADC and the LEE of the InGaN-based LEDs so far. As a result, the correlation between the ADC and the LEE of InGaN-Based LEDs is investigated in this dissertation.
The design and fabrication of 2-D PhCs and characterizations works are performed in the study. In optical measurement, micro-photoluminescence (μ-PL) measurements were used to provide comparison of the relative PL intensity. Integrating sphere (IS) measurements were used to decide the relative spectral radiant flux and also verify the trend observed in the μ-PL measurements. In addition, the characterizations of the LED devices were performed for extracting the light output power (LOP) and the far field radiation patterns of the LEDs. The finding first shows that the correlation between the ADC and the LEE of the 2-D PhCs LEDs is independent of the geometry and the shape of the 2-D PhCs, the LEE all reaches maximum value with the ADC of 51 % and has similar ADC dependent characteristic; besides, the LOP of the 2-D PhCs LEDs in hexagonal lattice arrangement (HLA) with the ADC of 51% are significantly improved by 81.9% as compared to the reference LED at an injection current of 350 mA; moreover, the better side-directional emission property of the 2-D PhCs LEDs in HLA than that in square lattice arrangement (SLA) has also been reported, which satisfies the requirement of display.
Subjects
空氣佔有率
電子束微影系統
發光二極體
光萃取增益
光子晶體
Type
thesis
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