p型掺杂晶体硅的低温液相(001)外延生长研究

Study of Low Temperature Liquid Phase(001) Epitaxy of p-type Doped Crystalline Silicon

为寻求以低成本制备n型太阳电池的pn结,进行了Al-17.6wt%Si合金熔体中(001)n型单晶硅衬底上液相外延生长p型掺杂硅实验。所用方法为垂直浸渍法,实验了过冷恒温生长与回熔处理后连续冷却生长两种模式,过程中体系以流动高纯氩保护。对所得外延生长晶体结构、形貌及所得pn结开路电压进行了分析和测定。结果显示,合金熔体中硅晶体(001)液相外延生长能够实现,但一般呈离散分布的金字塔型岛状生长;只有衬底回熔处理后原位连续降温生长模式可获得连续外延薄膜,之后在其上出现岛状生长,呈现Stranski-Krastanov生长模式。所得连续外延薄膜形成的pn结开路电压比恒温生长所得的提升约100 m V;连续外延薄膜形成后期出现的岛状生长使开路电压明显下降;生长速度提高会使连续降温外延生长pn结开路电压略有降低。

In pursue of a low cost method for fabrication of pn junctions of n-type solar cells, growth of a p-type doped crystalline silicon on （001） Si by means of low temperature liquid phase epitaxy from A1- 17.6wt% Si melt was attempted. A vertical dipping device with Ar circulated as ambient gas was used. Both isothermal growth and continuous cooling growth with melt-back treatment were experimented. Structure and topography of the obtained epitaxial crystals were examined. Open circuit voltages of the pn junctions formed were measured. The results show that, epitaxy in the A1-Si melt can be realized, but the growth is usually in pyramid-like island-pattern; only the continuous cooling growth after the melt-back treatment can generate a continuous epitaxial film. After that, island-pattern growth appeared on the film, indicating a Stranski-Krastanov growth mode. The open circuit voltages of the pn junctions formed in the continuous cooling growths are about 100 mV higher than those formed in the isothermal growths. The island growth after formation of the continuous epitaxial film remarkably reduced the open circuit voltage. Higher growth rate led to slightly lower open circuit voltage of the continuously grown pn junctions.