利用等离子体辅助分子束外延设备(P-MBE)在蓝宝石(Al2O3)衬底上外延生长ZnO薄膜,研究了不同生长温度对结晶质量的影响.随着生长温度的升高,X射线摇摆曲线(XRC)半高宽从0.88°变窄至 0.29°,从原子力显微镜(AFM)图像中发现薄膜中晶粒从20nm左右增大至200nm,室温光致发光(PL)谱中显示了一个近带边的紫外光发射(UVE)和一个与深中心有关的可见光发射.随着生长温度升高,可见光发射逐渐变弱,薄膜的室温载流子浓度由1.06×1019/cm3减少到7.66×1016/cm3,表明在高温下生长的薄膜中锌氧化学计量比趋于平衡,高质量的ZnO薄膜被获得.通过测量变温光谱,证实所有样品在室温下PL谱中紫外发光都来自于自由激子发射;随着生长温度的变化UVE峰位蓝移与晶粒尺寸不同引起的量子限域效应相关.
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