【摘要】 为了提高GaN基发光二极管(LED)的外量子效率,在蓝宝石衬底制作了二维光子晶体.衬底上的二维光子晶体结构采用激光全息技术和感应耦合等离子体(ICP)干法刻蚀技术制作,然后采用金属氧化物化学气相沉积(MOCVD)技术在图形蓝宝石衬底(PSS)上生长2μm厚的n型GaN层,4层量子阱和200nm厚的p型GaN层,形成LED结构.衬底上制作的二维光子晶体为六角晶格结构,晶格常数为3.8μm,刻蚀深度为800nm.LED器件光强输出测试结果显示,在PSS上制作的LED(PSS-LED)的发光强度普遍高于蓝宝石平面衬底上的LED,平均强度提高了100%.在PSS和蓝宝石平面衬底上GaN层的(0002)晶面采用X射线测得的衍射摇摆曲线显示,PSS上的GaN晶体质量并没有提高,表明PSS-LED外量子效率显著提高的原因不是由于内量子效率的提高,而可能是由于二维光子晶体产生的散射作用导致提取效率的提高所致.更多还原

【Abstract】 Investigation in fabricating two-dimensional (2D) photonic crystal (PC) on sapphire substrates for enhancing external efficiency of GaN based light emitting diodes (LEDs) is presented. 2D-PC was fabricated on a sapphire substrate using holographic lithography and inductively coupled plasma (ICP) dry etching. LEDs with 2?μm thick n-GaN layer,four pairs of InGaN/GaN quantum well structures and 200?nm thick p-GaN layer were grown on the patterned sapphire substrate (PSS) by metal organic chemical vapor deposition (MOCVD). The PC fabricated on PSS has 2D hexagonal lattice pattern,with 3.8?μm lattice constant and 800?nm depth. LED output measurement shows 100% increase in the average luminous intensity of PSS-LEDs compared with that of conventioanl LEDs. The measured X-ray rocking curves of (0002) diffraction for GaN layers grown on patterned and non-patterned sapphire substrates indicate that the quality of GaN crystal grown on PSS is not improved,which implies that the large enhancement of external quantum efficiency of PSS-LED is not caused by the increase in internal efficiency but possibly by the increase in extraction efficiency,which results from the scattering of the PSS.更多还原