p-GaN退火对InGaN量子阱光学性能的影响

Influence of p-GaN Annealing on Optical Properties of InGaN MQWs

近年来,N2退火和O2退火均被用于激活p-GaN中的Mg受主以提高p-GaN中的空穴浓度。基于两种退火技术,系统地研究了N2退火和O2退火对LED样品电学性能及光学性能的影响。电流电压特性的测试结果显示,在较低温度(500℃)下O2退火就可以达到与N2高温退火(800℃)相似的电学特性。变温光致发光测试表明,N2高温退火会在InGaN量子阱中形成In团簇,In团簇作为深的势阱增加了对载流子的束缚,能够将载流子更好地局限在势阱中。然而In团簇形成的同时也伴随着大量位错的产生,使其InGaN量子阱中的位错密度大幅度提高,因此室温下N2退火样品的辐射复合效率低于O2退火样品的辐射复合效率。

In recent years, thermal annealing in either N2 ambient or O2 ambient was used to activate the Mg-doped GaN epilayer and thus improve the density of holes in p-GaN. The electrical and optical properties of LED samples annealed in different ambient were systematically investigated. The test results of I-V characteristics show that samples annealed at low temperature （500 ℃ ） in O2 ambient and high temperature （800 ℃） in N2 ambient show similar current-voltage characteristics. The temperature-dependent photoluminescence （PL） measurement shows that high-temperature thermal annealing in N2 ambient can induce In clusters in InGaN muhiple quantum well （MQWs）. The deep traps induced by In clusters can work as localized centers which can enhance the confinement of carriers, the cavriers can be better boanded in well. However, there are much more dislocations out of the trap centers caused by high-temperature annealing, the dislocation density of InGaN MQWs increased significantly. Therefore, at room temperature, the radiative efficiency of the sample annealed in N2 ambient was lower than that annealed in O2 ambient.