氨热法GaN单晶生长的位错密度演变研究

Dislocation Density Evolution Study of GaN Single Crystal Growth by Ammonothermal Method

氮化镓单晶具有高击穿电压、直接带隙、高饱和电子漂移速率、良好的化学稳定性等特性,在光电子器件和大功率电子器件中有广泛的应用。然而异质外延氮化镓会产生高位错密度,限制了氮化镓基器件的性能发挥。本研究以HVPE-GaN为籽晶,采用氨热法生长了氮化镓单晶,利用扫描电子显微镜(SEM),光学显微镜和湿法腐蚀研究了氨热法氮化镓单晶籽晶区至侧向生长区的位错演变。研究结果表明,侧向生长区的氮化镓单晶位错密度明显低于籽晶区,侧向生长超过25μm后,位错密度降低2个数量级。

Gallium nitride(GaN)single crystal has the characteristics of high breakdown voltage,direct band gap,high saturated electron drift rate,good chemical stability,etc.,and has been widely used in optoelectronic devices and high-power electronic devices.However,the heteroepitaxial of GaN produces a high dislocation density,which limits the performance of GaN devices.In this study,GaN single crystal was grown by ammonothermal method using HVPE-GaN as a seed crystal.The dislocation evolution from the seed crystal region to the lateral growth region of GaN single crystal was studied by scanning electron microscopy(SEM),optical microscopy and wet etching.The results show that the dislocation density of GaN single crystal in the lateral growth region is obviously lower than that in the seed crystal region,and the dislocation density decreases by 2 orders of magnitude when the lateral growth exceeds 25μm.