LOW TEMPERATURE PREPARATION OF SIO2 TUNNEL OXIDES ON C SI WITH CHEMICALLY ABRUPT INTERFACES AND LOW DENSITIES OF DEFECT STATES

The combination of fast, non destructive, and surface sensitive spectroscopic methods, i.e. pulsed field modulated surface photovoltage SPV and quasi steady state photo conductance QSSPC , provided detailed information about the influence of wet chemical substrate preparation methods on the surface charge, energetic distribution of interfaces states Dit E on solar cell substrates and the resulting interface recombination losses on subsequent prepared ultra thin passivation layers. The SPV technique allows the measurement of the surface potential and determination of the interface state densities without any contact preparation. The results of these investigations could be successfully used to enhance the electronic properties of polished, saw damage etched and textured solar cell substrates with random pyramids by wetchemical smoothing and H termination procedures. As demonstrated for selected examples, this favourable effect can be preserved during the subsequent oxidation by thermalized atomic oxygen or during the soft plasma enhanced chemical vapor deposition PECVD of amorphous silicon a Si H . The resulting Dit E on ultra thin Si SiO2 layers and interface recombination losses on a Si H c Si hetero junctions were found to be significantly reduced compared to the standard RCA pre treatmen