图形化蓝宝石衬底上InGaN/GaN多量子阱发光二极管的光谱特性研究

Optical Characteristics of InGaN/GaN Light Emitting Diodes onPatterned Sapphire Substrate

运用电致发光(EL)和光致发光(PL)实验,分析了图形化蓝宝石衬底(PSSLEDs)和常规平面蓝宝石衬底(C-LEDs)InGaN/GaN多量子阱发光二极管的光谱特性。对比EL谱,发现PSSLEDs拥有更强的光功率和更窄的半峰宽(FWHM),说明PSSLEDs具有较高的晶体质量。其次,PSSLEDs的EL谱半峰宽随电流增加出现了更快的展宽,而这两种LED样品的PL谱半峰宽随激光功率增加呈现了基本相同的展宽变化,说明在相同电流下,PSSLEDs量子阱中载流子浓度更高,能带填充效应更强。另外,随着电流的增加,PSSLEDs和C-LEDs的峰值波长都发生蓝移,且前者的蓝移程度较小,结合半峰宽的对比分析,说明PSSLEDs量子阱中的极化电场较小。最后,对比了PSSLEDs和C-LEDs的外量子效率随电流的变化,发现PSSLEDs拥有更严重的efficiency droop,说明量子阱中极化电场不是导致efficiency droop的主要原因。

In the present paper,optical characteristics of InGaN/GaN multiple quantum well s light emitting diodes fabricated on the conventional（C-LEDs） and patterned sapphire substrates（PSSLEDs） were investigated by electroluminescence（EL） and photolum i nescence（PL）.PSSLEDs show higher light output power and smaller full width at half maximum（FWHM） of EL than those of C-LEDs for their better crystalline qu ality.The FWHM of EL for PSSLEDs exhibits faster broadening as current increas es than C-LEDs,while the same broadening of FWHM of PL as excitation power inc reases is shown in PSSLEDs and C-LEDs,which indicate that there is stronger ba nd filling effect in PSSLEDs caused by relatively higher carrier density in thei r QWs at the same current injection level.Besides,smaller blue-shift of peak wa velength of EL as injection current increases in PSSLEDs suggests that piezoelec tric field in PSSLEDs is weaker than that in C-LEDs.Therefore,comparing the changes in external quantum efficiency as current increases for PSSLEDs and C-L EDs,more serious efficiency droop for PSSLEDs could not be mainly caused by pie zoelectric field in QWs.