利用次微米級圖形化藍寶石基板製作氮化銦鎵-氮化鎵發光二極體之研究

Abstract

本研究中，我們利用光阻熱回流技術可以製作出圖案為具有次微米間距，柱狀並帶有45°傾斜角度圖形的高密度圖案化藍寶石基板，並將其應用在波長為475-nm的氮化銦鎵/氮化鎵發光二極體結構發光二極體的元件上。高密度圖案化藍寶石基板和一般藍寶石基板相較之下，可以提高磊晶的品質。經由高解析度X光繞儀的分析，磊晶成長在高密度圖案化藍寶石基板和一般藍寶石基板的(102)平面，晶體轉動曲線的半高寬分別為540與280 arcsec。而在高密度圖案化藍寶石基板上的成長的發光二極體製作成元件(元件大小350×350 µm2)時，施與20mA的電流下，電壓與發光亮度分別為3.8V及96.6mcd，較成長在一般藍寶石基板上的發光二極體元件亮度增加79%。原因除了高密度圖案化藍寶石基本擁有較佳的磊晶品質外，帶有45°傾斜角度的圖案也能增加元件內部光的淬取效率，進而增加發光二極體的亮度。

475-nm InGaN/GaN light-emitting diode (LED) structure successfully grown and fabricated on high density patterned sapphire substrate (PSS). Sub-micron fine pattern and inclined facet 45° pillar ideal for PSS was achieved using thermally reflow technique. GaN grown on such substrate has good crystalline quality, as observed from HRXRD. The full width at half maximum (FWHM) of the (102) plane rocking curve for GaN grown on flat sapphire substrate and PSS are 540 and 280 arcsec, respectively. Such improvement is thought to be due to the elimination of the threading dislocation density. For 350×350 µm2 PSS LED operating at the forward current of 20mA under room temperature, the forward voltage of 3.8V, the light emitting intensity is found to be 96.6mcd. Compared with the LED on the flat substrate, there was a drastic enhancement on brightness. This improvement could be attributed to the better quality of the material and increase of the light extraction by the inclined facet of the pillar pattern.