Comparative study of LPE and VPE silicon thin film on porous sacrificial layer

Thin film single crystal silicon on foreign substrate is an attractive way to realize cheap and efficient photovoltaic devices. In this paper we will compare epitaxial growth of silicon thin film on double porous sacrificial layers obtained by liquid or vapor phase epitaxy (LPE or VPE). Porous silicon is formed by electrochemical anodisation of monocrystalline silicon in a HF/ethanol solution. VPE is achieved in an atmospheric pressure chemical vapor deposition (APCVD) reactor under H 2 atmosphere. Growth rate is in between 0.5–3 μm/min. LPE is realised in a graphite sliding boat using indium or tin as solvent. Growth rate is in the range 0.1–1 μm/min depending on the temperature, the cooling rate and the solvent. We discuss the substrate orientation, temperature, growth rate, layer homogeneity and electrical properties of the epilayers for both growing techniques. Diffusion length and mobility are measured respectively with LBIC and Hall effect technique. The values obtained for p-type (μ>100 V/cm 2/s and L n>100 μm) allows the realisation of solar cell using interdigitated technology on the top of this layer, which is detached and transferred onto mullite substrate.