氮掺入对N型纳米硅薄膜微观结构及光电特性影响

采用等离子体增强化学气相沉积技术(PECVD)通过改变NH₃流量制备出不同含氮量N型富硅氮化硅硅薄膜。利用Raman散射、红外吸收、紫外-可见光分光光度计及暗态I-V测量等技术分析了氮掺入对薄膜微观结构以及光电特性的影响。结果显示，随着NH₃的增加，薄膜由微晶硅向纳米硅结构转变，薄膜中晶粒尺寸减少，晶化度降低，微观结构有序性降低，所对应薄膜光学带隙增大，而带尾分布变窄。同时，红外吸收谱分析表明，Si—N键合密度增加，P掺杂受阻。暗态I-V测量显示，薄膜电导率随着NH₃掺入整体较微晶硅降低，但随NH₃增加，电导率受到迁移率和载流子浓度等特征共同作用先降低后变大，揭示了影响薄膜电导率的机制存在一定的竞争，然而过高的非晶网络结构将增大载流子的复合导致薄膜电导率显著降低。

Effect of the Nitrogen Incorporation on the Microstructure and Photoelectric Properties of N Type Nanocrystalline Silicon Thin Films

N type silicon-rich nanocrystalline-SiNx∶H films were prepared by plasm a enhanced chemical vapor deposition technique by changing NH3 flow rate.The effect of nitrogen incorporation on the microstructure and photoelectric propert ies of the thin films were characterized by Raman,Fourier transform infrared sp ectroscopy,ultraviolet-visible absorption spectra,and Hall effect measurement.The results indicated that with the increasing NH3,a phase transition from microcrystalline to amorphous silicon occured.Transmission electron microscope observation revealed that the size of silicon quantum dots could be adjusted by varying the flow rate of NH3.The microstructure order of the films reduced wi th increasing the flow rate of NH3,while the optical band gap increased,and the optical band tail became narrow.Meanwhile,Si-N bonds density increased an d P doping was blocked.I-V testing results showed that with increasing NH3,the conductivity of films first decreased compared with nanocrystalline-Si and then increased.These behaviors reveal a competition in the mechanisms controlli ng the conductivity.However,with further increasing NH3,the conductivity de creased significantly due to rapid carrier recombination on the amorphous net st ructure.