A Study on the Application of Different Patterned Sapphire Substrate for GaN Light-Emitting Diodes

• Main Authors: Chieh-Nan Tseng, 曾介南
• Other Authors: Han-Wen Liu
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/71141804504238701744

碩士 === 國立中興大學 === 光電工程研究所 === 101 === In this research, the patterned sapphire substrates, were fabricated by the dry etching、wet etching and two-step wet etching and were used to make the blue ray LED respectively. And the SEM was used to inspect the pattern size, etching depth and pattern morphology in these processes. Besides, the optical and electrical properties, such as forward I-V curve、leakage current, the relationships between the wavelength and power, the current spreading and output power of Ag-TO packaging, were measured by the TLM system、prober、spectrometer and integrating sphere to compare the difference between these processes. We designed three different conditions to investigate the properties among these processes. According to the experiment results, the luminance was mainly determined by the pattern size, etching depth and taper. The large etching depth and pattern taper, and the smaller pattern size would improve the luminance of a blue ray LED. The dry etching process had a better stability and etching uniformity, but it also suffered some disadvantages such as higher cost, less capacity and more difficult to control the selectivity. As compared with the wet etching process, we also found out that the output power could be improved about 5 to 7 % and the leakage current could decrease about 23nA in the secondary wet etching one by changing the number and angle of etching pattern: Besides to compare with dry etching process, the output power could be improved about 8%. In conclusion, the efficiency of the blue ray LED on patterned sapphire substrate fabricated by the two-step wet etching process could be improve by changing the pattern taper and increasing the number of the taper to achieve the better optical and electrical properties.