Optical and Structural Properties of Cr-Doped GaN Grown by HVPE Method

Single crystalline Cr-doped GaN fihns are successfully grown by hydride vapor phase epitaxy. The structure analysis indicates that the film is uniform without detectable Cr precipitates or clusters and the Cr atoms are substituted for Ga sites. The impurity modes in the range 510 530cm^-1 are observed by the Raman spectra. The modes are assigned to the host lattice defects caused by substitutional Cr. The donor-aeceptor emission is found to locate at Ec - 0.20 eV by analyzing the photoluminescence spectrum obtained at different temperatures, and the emission is attributed to the structural defects caused by CrGa-VN complex. The superconductor quantum interference device results show that the Cr-doped GaN film without detectable Cr precipitates or clusters exhibits paramagnetic properties.     

立式氢化物气相外延反应器生长GaN模拟研究

利用有限元法对立式氢化物气相外延系统工艺参数进行了优化, 发现在新设计的立式氢化物气相外延反应器中, 存在衬底与气体入口的最佳距离, 在最佳距离位置上, 沉积的均匀性最好. 在设定的条件下模拟的结果表明这个距离为5 cm. 在此基础上, 模拟得到了优化的生长参数. 模拟的结果还表明重力方向与GaCl气体出口方向的夹角的大小, 对GaN沉积的速率和均匀性影响很大. 重力方向与GaCl气体出口方向相反时得到的计算结果与两者方向相同时得到的计算结果比较, 尽管GaN沉积速率有所下降, 但是沉积均匀性却得到了极大的改善. 此外还讨论了浮力效应对GaN沉积的影响.