多孔硅的制备及其吸杂处理对电学性能的影响

多孔硅吸杂是减少晶体硅中杂质和缺陷,提高太阳能电池转换效率的有效方法。采用电化学腐蚀方法在单晶硅片上制备多孔硅,通过观察多孔硅的形貌、结构及单晶硅片的电阻率变化,研究不同电流密度制备的多孔硅对吸杂效果的影响,并从多孔硅的结构出发探究多孔硅吸杂的机理。结果表明,随电流密度增加,孔隙率明显增加,多孔硅在电流密度为100mA/cm2时,孔隙率最大;电流密度越大,多孔硅伴随所产生的弹性机械应力增加,晶格常数相应增加,这两个因素都有利于缺陷和金属杂质在多孔硅层-基底界面处迁移和富集,导致单晶硅吸杂后电阻率增大。

Preparation of Porous Silicon and the Influence of Gettering on the Electrical Properties

Porous silicon gettering was an effective method for reducing impurities and defects in crystalline silicon and improving conversion efficiency of solar cell.Porous silicon layer was prepared on the surface of monocrystalline silicon by electrochemical etching.The characterizations of porous silicon layer were investigated and the effect on the porous silicon gettering of current density.Moreover,the gettering mechanism was supposed based on the microstructure of porous silicon.The result showed that the porosity increased significantly as the current density increasing and the maximum values are achieved for the current density 100mA/cm2.The porous silicon layer formation was accompanied by the appearance of elastic mechanical stress and the increasing of lattice parameters.The two factors were beneficial to the migration for defects and metallic impurities from the bulk to the PS layer.Therefore,the resistivity increased with the current density increasing.