多孔硅微腔微结构的AFM和SEM研究

Analysis on Microstructure of Porous Silicon Microcavities with AFM and SEM

多孔硅微腔是采用交替变化脉冲腐蚀电流密度的方法制成的多孔度周期性变化的多孔硅结构。用原子力显微镜 (AFM )和扫描电子显微镜 (SEM )对多孔硅微腔的侧向解理的截面进行了观测 ,得到了不同多孔层及其界面处的图像。微腔截面的扫描电镜图像清楚地显现出第Ⅱ型多孔硅微腔的“三明治”结构 ,即中心发光层被夹在两个Bragg反射镜之间。

Porous silicon microcavities were etched with alternate varied current density which made the porosity change periodically.By using atomic force microscopy(AFM) and scanning electron microscopy(SEM) to investigate the cross section of the porous silicon microcavity structure,images of different layers with different porosity are obtained.SEM photograph of the porous silicon microcavities clearly shows the sandwich structure,in which an active layer is included between two distributed porous silicon Bragg reflectors.By carefully adjusting the growth and the etching parameters such as the thickness of the silicon epitaxy layers, the etching current density and the etching time,the wavelength of the narrow photoluminescence peaks can be tuned over a wide wavelength range of visible light. These results reveal that the porous silicon microcavities can be easily fabricated by electrochemical etching of MBE grown silicon multi layers.