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

摘要

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 wells light emitting diodes fabricated on the conventional (C-LEDs) and patterned sapphire substrates (PSSLEDs) were investigated by electroluminescence (EL) and photoluminescence (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 quality. The FWHM of EL for PSSLEDs exhibits faster broadening as current increases than C-LEDs, while the same broadening of FWHM of PL as excitation power increases is shown in PSSLEDs and C-LEDs, which indicate that there is stronger band filling effect in PSSLEDs caused by relatively higher carrier density in their QWs at the same current injection level. Besides, smaller blue-shift of peak wavelength of EL as injection current increases in PSSLEDs suggests that piezoelectric 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-LEDs, more serious efficiency droop for PSSLEDs could not be mainly caused by piezoelectric field in QWs.