Merkel, J.J.; Sontheimer, T.; Rech, B.; Becker, C.: Directional growth and crystallization of silicon thin films prepared by electron-beam evaporation on oblique and textured surfaces. Journal of Crystal Growth 367 (2013), p. 126-130
Electron-beam evaporation (EBE) of silicon permits the high-rate deposition of photovoltaic thin-film devices at low costs. The directional, non-conformal growth characteristic of EBE is systematically investigated by varying the silicon flux angle of incidence γ on the substrate surface between 0° and 49°. After solid phase crystallization the micro-structural properties of these silicon films are investigated and correlated with the electronic quality of n+/p-/p+-type solar cell stacks. As γ exceeds 30°, the porosity and oxygen content of the silicon films increase significantly which is accompanied by a break-down of the electronic material quality. At γ > 40° the silicon crystallization process is even found to be suppressed resulting from a columnar film morphology infiltrated by oxygen-reach pores. The knowledge of this critical angle is essential when textured substrates, consisting of many tilted micro-areas, are used for enhanced light absorption in high-quality silicon films. Furthermore, the inclination angle γ can serve as design parameter for tailored substrate templates for the fabrication of advanced light-harvesting structures by self-organized solid phase crystallization.