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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.
In order to improve the external quantum efficiency of GaN-based light-emitting diodes (LEDs), two-dimensional photonic crystals were fabricated on sapphire substrate.The two-dimensional photonic crystal structure on the substrate was fabricated by laser holography and ICP dry etching Then, a 2 μm-thick n-type GaN layer, a 4-layer quantum well and a 200 nm-thick p-type GaN layer were grown on a patterned sapphire substrate (PSS) using metal oxide chemical vapor deposition (MOCVD) to form an LED structure. The two-dimensional photonic crystal fabricated on the substrate has a hexagonal lattice structure with a lattice constant of 3.8 μm and an etching depth of 800 nm. The LED intensity output test results show that the LED (PSS-LED) The intensity is generally higher than that of LEDs on sapphire planar substrates, with an average intensity increase of 100%. The (0002) crystal planes of the GaN layer on PSS and sapphire planar substrates using X-ray diffraction rocketing curves show that GaN on PSS The crystal quality did not increase, indicating that the reason for the significant increase in external quantum efficiency of PSS-LED is not due to the increase of internal quantum efficiency, but rather the increase of extraction efficiency due to the scattering effect caused by two-dimensional photonic crystal.