Growth on Multicrystalline Si Substrates

For solar cell applications, thin film LPE is economically viable only if it is combined with a low-cost multicrystalline Si substrate (high-throughput silicon ribbons, upgraded metallurgical grade silicon MG-Si) or with a foreign substrate (glass, ceramic, metallic sheet... see section 9-7). 

Good-quality multicrystalline silicon (mc-Si) has been used as a model to develop techniques for depositing silicon on silicon. Grain boundaries 

Wagner compared structural and electrical properties of polycrystalline Si layers grown by CVD or LPE (In melt, 947°C, 0.12 pm min-1) with similar grain boundary structures [20]. The measured minority carrier lifetime was always higher and the recombination strength of the defects was smaller in the LPE layers than in the CVD layers. They attributed this to the higher purity of the LPE layer and its lower density of defects (rod-like defects). 

The left part of the Fig. 9.4 presents the growth by equilibrium cooling on mc-substrates and the resulting epitaxial layer and the right, with y°y° technique. 

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