MOCVD GaN/InN/GaN量子阱的应变表征

Strain State of MOCVD InN/GaN Quantum Wells

采用MOCVD外延生长11周期InN/GaN量子阱结构样品,原子力显微镜表面形貌结果显示实现了台阶流动生长模式.通过高分辨率X射线衍射与掠入射X射线反射谱技术获得了阱层与垒层的实际厚度.从(102)非对称衍射面与(002)对称衍射面的倒异空间图,确认了InN阱层处于与GaN共格生长的完全应变状态,获得了GaN缓冲层的晶体质量信息及其c轴与a轴晶格常数,确认外延层因受衬底热失配的影响处于压应变状态.

Step flow growth has been observed on the surface morphology of eleven periods InN /GaN quantum well structure grown by MOCVD.The high-resolution x-ray diffraction results have been combined with reflectivity data to evaluate the layer thickness of InN and GaN.The asymmetric（102） reflection and symmetric（002） reflection reciprocal space map show that a-axis lengths of both InGaN well layers and GaN templates are identical.It is confirmed that InN / GaN MQWs structure of the sample is grown coherently on GaN templates.The c-axis and a-axis lengths of GaN buffer layer show that it is compressed,due to the thermal strain which is originated from the difference in thermal expansion coefficients between GaN epilayers and sapphire substrates during cooling from the growth temperature to room temperature.