Current-voltage characteristics of n-amorphous low-pressure chemical vapor deposited silicon films on p-crystalline silicon

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Heterojunction devices have been fabricated by a low-pressure chemical vapor deposition technique whereby n-type amorphous or microcrystalline silicon films were grown on p-type crystalline silicon substrates. Heterostructures produced under various conditions of thin film deposition were subjected to detailed I-V curve analysis. It is seen that for amorphous-crystalline heterojunctions the current transport is through tunneling in the low bias range and limited by electron-hole recombination in the high bias range. For the microcrystalline-crystalline junctions however, recombination current at the interface dominates the current transport process. Illuminated I-V curves corresponding to films deposited at different substrate temperatures (Ts ) and dopant gas-to-silane ratios (R) show that the high values of the short-circuit current (Isc), open-circuit voltage (Voc ), and fill factor (FF) are achieved at values close to Ts ∼620 °C and R ∼4×10−3 in conformance with dark I-V characteristic data.