GaN外延层中的缺陷研究

DEFECTS IN GaN EPILAYERS 

采用阴极射线致发光法观察金属有机物汽相外延法生长的具有不同表面形貌的ＧａＮ外延层中黄色发光带的强度分布．结果表明六角金字塔形表面形貌对发光强度分布的测量有很大影响．测量和比较表面镜面加工样品的黄色发光带强度分布、原子序数衬度和Ｘ射线波谱发现，黄色发光带的强度在含有Ｏ和Ｃ等杂质缺陷附近较强．高分辨透射电子显微镜观察表明，杂质缺陷区的晶格结构不同于ＧａＮ基质，以及位错和裂缝等由应力引起的缺陷．认为此类缺陷可能是生长过程中。

Abstract The intensity distribution of a yellow luminescence band was observed by cathodoluminescence (CL) on GaN epilayers with different surface morphologies grown by metallorganic vapor phase epitaxy, which showed that the hexagonal hillock surface morphology had an effect on CL image of the yellow luminescence band. The polished epilayers were further investigated by CL image,atomic number contrast,and wavelength dispersive X ray spectrometry,and were observed that the intensity of the yellow luminescence band was relatively strong around the defects associated with impurities of O,C,and so on.The lattice images of high resolution transmission electron microscope exhibited the structures of the defects different from that of GaN matrix,misfit edge dislocations and cracks.The results suggest that the defects may result from the precipitations in the V shape grooves of imperfect coalescence during epitaxy.