脉冲激光双光束沉积掺Mg的GaN薄膜的研究

Pulsed Laser Two-Beam Deposition of Mg-Doped GaN Thin Films

采用脉冲激光双光束沉积系统在Si(111)衬底上生长了掺Mg的GaN薄膜和未掺杂GaN薄膜。利用X射线衍射 (XRD)、原子力显微镜 (AFM)、室温范德堡霍尔测量及光致发光 (PL)光谱对两类薄膜进行对比分析 ,结果显示 ,所生长的GaN薄膜均为六方纤锌矿晶体结构 ,掺Mg可细化所生长的GaN薄膜晶粒。随着掺Mg量的增加 ,GaN薄膜无需后处理即可由n型导电转化为 p 型导电 ,GaN薄膜的光学性能随 p型载流子浓度增大而提高 ;然而掺Mg却导致GaN薄膜结晶质量下降 ,掺镁量过大的GaN薄膜中 p 型载流子浓度反而减少 ,光致发光中黄发射峰增强较大。研究表明通过优化脉冲激光双光束沉积参数无需任何后处理可直接获得高空穴载流子浓度的 p

The GaN thin films were grown on Si(111) substrate by Mg-doping simultaneously using a pulsed laser two-beam deposition system. The characteristics of an undepoed GaN film and the Mg-doped GaN film were investigated by using X-ray diffraction, atomic force microscopy, room temperature Van der Pauw-Hall measurements and photoluminescence. It was found that the Mg-doped GaN films have the hexagonal wurtzite crystalline structures similar to the undoped GaN films. As increasing the doped Mg-doped dose, a decrease in the size of grains of the GaN films can be seen, and the GaN films become p-type conductivity. The optical property of Mg-doped GaN film can be improved with increasing p-type carrier concentration. But the p-type carrier concentration can be decreased and the crystalline quality of the GaN films can be degraded by the too high doping Mg dose. The intensity of the yellow band emission peaks become stronger with increasing the doping Mg dose. These results show that it is possible to obtain high p-type carrier concentration in GaN films using the optimal pulsed laser two-beam deposition parameters.