沉积参数对MOCVD法生长的Al_xGa_(1-x)N薄膜性能有很大的影响.利用高分辨XRD,紫外-可见透射光谱,原子力显微镜,扫描电子显微镜和荧光光谱研究了沉积温度对低压MOCVD沉积的高Al含量的Al_xGa_(1-x)N外延膜缺陷密度以及发光性能的影响.结果发现,随着沉积温度的升高,Al_xGa_(1-x)N薄膜中的螺型位错密度减少,但是刃型位错密度增加,因此简单地改变沉积温度并不能降低总的位错密度以及提高薄膜的发光性能.进一步地分析测试结果表明,随着沉积温度的升高,Al_xGa_(1-x)N薄膜内的Al含量增加,导致禁带宽度增大和发光波长的蓝移,因此适当提高沉积温度(1000～1050℃)是获得高Al含量Al_xGa_(1-x)N薄膜的一种有效手段,但是过高的沉积温度(>1100℃)不利于提高薄膜的发光强度.
Deposition parameters are important to the characteristics of the Al_xGa_(1-x)N films. Effects of the deposition temperature on the defects densities and the photoluminescence of the Al_xGa_(1-x)N films with high Al content were investigated, which is deposited by low pressure MOCVD on sapphire. High resolution XRD,UV-Visible transmittance, AFM, SEM, and photoluminescence spectroscope were used to characterize the Al_xGa~(1-x)N films with high Al content. It is found that as the growth temperature increases, the screw disloca-tion density in Al_xGa_(1-x)N films increases, while the edge dislocation density decreases. So simply increasing deposition temperature is not a good way to reduce the total defects density or enhance the photoluminescence of the high Al content Al_xGa_(1-x)N films. Further analysis shows that higher deposition temperature is beneficial to achieve high Al content Al_xGa_(1-x)N films. It's found that as the deposition temperature increases, Al con-tent in Al_xGa_(1-x)N films also increases, which results in the increase of the bandgap of the films. Therefore,moderately increasing the deposition temperature (1000-1050℃)is an effective way to increase Al content in Al_xGa_(1-x)N films. Nevertheless, too higher deposition temperature (> 1100℃) is detrimental for the pho-toluminescence of the Al_xGa_(1-x)N films.
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