GaN buffer layers (thickness ～60nm) grown on GaAs(001) by low-temperature MOCVD are investigated by X-ray diffraction pole figure measurements using synchrotron radiation in order to understand the heteroepitaxial growth features of GaN on GaAs(001) substrates.In addition to the epitaxially aligned crystallites,their corresponding twins of the first and the second order are found in the X-ray diffraction pole figures.Moreover,{111} φ scans with χ at 55° reveal the abnormal distribution of Bragg diffractions.The extra intensity maxima in the pole figures shows that the process of twinning plays a dominating role during the growth process.It is suggested that the polarity of {111} facets emerged on (001) surface will affect the growth-twin nucleation at the initial stages of GaN growth on GaAs(001) substrates.It is proposed that twinning is prone to occurring on {111}B,N-terminated facets.
采用 Al N插入层技术在 Si(1 1 1 )衬底上实现无微裂 Ga N MOCVD生长 .通过对 Ga N外延层的 a,c轴晶格常数的测量 ,得到了 Ga N所受张应力与 Al N插入层厚度的变化关系 .当 Al N厚度在 7～ 1 3nm范围内 ,Ga N所受张应力最小 ,甚至变为压应力 .因此 ,Ga N微裂得以消除 .同时研究了 Al N插入层对 Ga N晶体质量的影响 ,结果表明 ,许多性能相比于没有 Al N插入层的 Ga
