V形坑尺寸对硅衬底InGaN/AlGaN近紫外LED光电性能的影响

摘要

使用MOCVD在图形化Si衬底上生长了InGaN/AlGaN近紫外LED,通过改变低温GaN插入层的厚度调控V形坑尺寸,系统地研究了V形坑尺寸对InGaN/AlGaN近紫外LED(395 nm)光电性能的影响.结果表明,低温GaN插入层促进了V形坑的形成,并且V形坑尺寸随着插入层厚度的增加而增大.在电学性能方面,随着V形坑尺寸的增大,-5 V下的漏电流从5.2×10-4 μA增加至6.5×102 μA;350 mA下正向电压先从3.55 V降至3.44 V,然后升高至3.60 V.在光学性能方面,随着V形坑尺寸的增大,35 A/cm2下的归一化外量子效率先从0.07提高至最大值1,然后衰退至0.53.对V形坑尺寸影响InGaN/AlGaN近紫外LED光电性能的物理机理进行了分析,结果表明:InGaN/AlGaN近紫外LED的光电性能与V形坑尺寸密切相关,最佳的V形坑尺寸为120~190 nm,尺寸太大或者太小都会降低器件性能.%InGaN/AlGaN near-ultraviolet light emitting diode (near-UV LED) were grown on patterned Si substrate by metal-organic chemical vapor deposition (MOCVD).The effects of V-pit size on optical and electrical properties of InGaN/AlGaN near-UV LED (395 nm) were investigated systematically by manipulating the thickness of low temperature GaN interlayer to change the V-pit size.The results show that the low temperature GaN interlayer can enhance the formation of V-pit, and the V-pit size increases with the increasing of the thickness of low temperature GaN interlayer.In terms of electrical properties, with the increasing of the V-pit size, the leakage current at -5 V increases from 5.2×10-4 μA to 6.5×102 μA, and the forward voltage at 350 mA decreases from 3.55 V to 3.44 V initially and then increases to 3.60 V.In terms of optical properties, with the increasing of the V-pit size, the normalized external quantum efficiency (EQE) at 35 A/cm2 increases from 0.07 to the maximum of 1 initially and then decreases to 0.53.The mechanism of the effects of V-pit size on optical and electrical properties of InGaN/AlGaN near-UV LED were analyzed.The analyzing results show that the optical and electrical properties of InGaN/AlGaN near-UV LED are closely related to V-pit size.The optimized V-pit size is approximately 120-190 nm, too large or too small will deteriorate the properties of devices seriously.