IMPLANTED BURIED LAYERS AND INTERFACES - APPLICATION IN THE NEW AREA OF VERY-HIGH AND ULTRA-HIGH EFFICIENCY SOLAR-CELLS

Today any real progress in solar cell conversion efficiency necessitat es new device concepts, new materials (with global and local modificat ions), new technological approaches and development, Very promising re sults have been obtained by ion implantation of Si conjugated with an adequate thermal treatment. In this paper an example of doping impurit y implantation for a multi-interface emitter formation is presented. T his approach allows simultaneous formation of: i) an inserted layer wi th amorphized structure and two hetero-interfaces of the alpha-Si/c-Si type, ii) a doping-impurity profile of the emitter, iii) a collecting P-N junction and iv) a post implantation defect gettering. One of the more important questions concerns the structural, optical and electro nic quality of alpha-Si/c-Si buried interfaces, This aspect has been c arried out by an investigation of implantation conditions (energy, dos e, temperature) and of the thermal treatment that forms definitively t he buried nanostructure and its solid epitaxy neighborhood. The simpli fied devices with inserted sub-structures have been characterized by t hree types of techniques: structural (RBS, Raman spectroscopy), physic o-chemical (SIMS) and electrical (spreading resistance profile).