Characterization of Optical and Frequency Responses of InGaN/GaN Nanorod Light Emitting Diodes
Date Issued
2013
Date
2013
Author(s)
Tan, Jin-Yi
Abstract
Recently, GaN-based wide bandgap light emitting diodes (LEDs) have been intensively developed and put applications in solid-state lighting and communication due to its superior optical and electrical characteristics. The InGaN/GaN nanorod light-emitting-diode array is one of the most popular structures. In this thesis, we demonstrated a novel and practical approach to fabricate InGaN/GaN nanorod LED arrays with p-i-n structure using nanosphere lithography for nanorod formation, PECVD (plasma-enhanced chemical vapor deposition) grown SiO2 layer for sidewall passivation, and chemical mechanical polishing (CMP) process for parallel metal contact. The nano-structure device has been proved to relax the compressive strain underneath the active layers effectively.
Nowadays, a commonly employed method to find IQE of a LED is by assuming complete frozen of defects at very low temperature and thus the IQE to be 100%. Despite the simplicity, the method may have underestimates other factors for IQE. According to our temperature-dependent Raman measurement, there is a severer strain effect accompanying the eliminating defects with decreasing temperature. Thus, we proposed a method by taking both defects and strain into consider and figured out more accurate IQE. We further discussed the external quantum efficiency and the light extraction efficiency on planar and nanorod LEDs.
Another potential application of LEDs is for visible light communications (VLC) system, which is a rapidly growing research technology. Together in this work, nanorod and planar devices with different mesa area were fabricated to explore frequency response on the E-O modulation bandwidth. With a diameter in nanoscale, the p-i-n diode arrays may have advantages in strain relaxation and confinement of carrier transport due to spatial separation of nanorod which may lead to a shorter carrier lifetime thus faster response speed in nanorod LEDs. These properties in nano-structure LEDs may be further used for application in VLC system both in free space and fiber-based embodiments.
Subjects
氮化鎵
奈米柱
發光二極體
內部量子效率
光萃取效率
應力釋放
化學機械研磨
可見光通訊
電光調製帶寬
載子壽命
Type
thesis
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