Recombination behavior and contact resistance of n+ and p+ poly-crystalline Si/mono-crystalline Si junctions

We present an investigation of the electrical characteristics – recombination and contact resistance – of poly-crystalline (poly) Si/mono-crystalline (c) Si junctions and of the influence of the interfacial oxide between the poly-Si and the c-Si on these characteristics. In particular, we compare thermally grown oxides with different thickness values with wet chemically grown oxides. Both n- and p-type poly-Si emitters are investigated. For one combination (n-type poly-Si, thermal oxide), we compare planar and textured surfaces. For all oxide types investigated, we achieve combinations of low recombination current densities <20 fA/cm² and low specific contact resistances <0.1 Ω cm². The corresponding implied open-circuit voltages measured on our test structures are 732 mV (n-type poly-Si) and 711 mV (p-type poly-Si). By applying these poly-Si layers on a solar cell structure, we achieve an open-circuit voltage of 714 mV and a series resistance of 0.6 Ω cm².