Ultraviolet/blue Light-Emitting Diodes Based on Single Horizontal ZnO Microrod/GaN Heterojunction

• Main Authors: Chia-FongDu, 杜佳峰
• Other Authors: Hsu-Cheng Hsu
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/76309554743496192923

碩士 === 國立成功大學 === 光電科學與工程學系 === 102 === Zinc oxide (ZnO) is a wide band gap semiconductor (3.37 eV) and its large exciton binding energy of 60 meV makes free excitons stable even at room temperature. Thus it has been suggested that ZnO has enormous potential for developing blue lasers and light emitting diodes. Therefore, we used a chemical vapor deposition method to produce zinc oxide microrod (MR) and combine with the P-type gallium nitride (p-GaN) thin film to form the hybrid light-emitting diode. In the experiment, we fabricated the light-emitting diodes simply by a stacked manner. According to the results, we found out that the growth of a single ZnO microrod by chemical vapor deposition has the hexagonal cross section and smooth side facets, and also with single crystalline wurtzite ZnO structure by scanning electron microscope (SEM) and raman spectrum system. Then, we study the ZnO MR/p-GaN hybrid light-emitting diode to realize the current characteristics, optical properties and the electron transport mechanism. The emission from the device can be found under the both forward and reverse bias. Especially, the light emitted under reverse bias has a strong blue-violet light. Therefore doing more in-depth study on the device which was operated under the reverse bias, we found that the emission enhance is attributed to electron tunneling effect. By the theory and mathematical model, we can prove electron tunneling effect caused by the zinc oxide defects which can capture the electron into the deep-level states and make it easier for the electron can tunneling from the deep-level states to the conduction band in n-ZnO. This mechanism can increase the recombination in the ZnO and enhance its near band edge emission.