垒温对硅衬底GaN基蓝光LED发光效率的影响

用MOCVD技术在硅衬底上生长了GaN基蓝光LED外延材料,研究了有源层多量子阱中垒的生长温度对发光效率的影响,获得了不同电流密度下外量子效率(EQE)随垒温的变化关系。结果表明,在860~915℃范围内,发光效率随着垒温的上升而上升。当垒温超过915℃后,发光效率大幅下降。这一EL特性与X光双晶衍射和二次离子质谱所获得的阱垒界面陡峭程度有明显的对应关系,界面越陡峭则发光效率越高。垒温过高使界面变差的原因归结为阱垒界面的原子扩散。垒温偏低使界面变差的原因归结为垒对前一个量子阱界面的修复作用和为后一个量子阱提供台阶流界面的能力偏弱。外延生长时的最佳垒温范围为895~915℃。

Dependence of Electroluminescence on Barriers Temperature in GaN Base Blue LED on Silicon Substrate

The growth of GaN-based blue LED with different barriers temperature in multiple quantum wells on silicon substrate by MOCVD method was reported. The dependence of luminescence on barriers temperature was obtained. The relationship between external quantum efficiency (EQE) and barriers temperature under different current density showed that EQE increases with barriers temperature during the temperature from 860 to 915 ℃, and then EQE decreases a lot after the temperature over 915 ℃. The results of XRD, SIMS and EL support each other very obviously, which means that the luminescence efficiency is contributed on the sharpness of well-barrier interface. Over top temperature of barriers will result in a worse sharpness of well-barrier interface owing to an undesirable atoms diffusion. Much lower temperature of barriers will also cause a worse sharpness of well-barrier due to the non-step flow growth of barriers. The optimization barriers temperature range is from 895 to 915℃ for epitaxy growth.