Carrier transport properties of flash-lamp-crystallized poly-Si films

We have investigated carrier transport properties of μm-order-thick polycrystalline silicon (poly-Si) films formed by flash lamp annealing (FLA) of precursor amorphous Si (a-Si) films on glass substrates. The Hall mobility of flash-lamp-crystallized (FLC) poly-Si films decreases as doping concentration increases, and then reversely increase with further increase in doping concentration, both in the cases of p- and n-type poly-Si films. The tendency observed is characteristic of poly-Si materials having a number of grain boundaries at which carriers are trapped. N₂-atmosphere furnace annealing of FLC poly-Si films with low doping concentration significantly recovers their carrier concentration and improve their carrier mobility up to more than 10 cm²/Vs, which is probably because of the termination of the trapping states by hydrogen (H) atoms that exists in FLC poly-Si films on the order of 10²¹/cm³. The realized mobility of FLC poly-Si films exceeds those of conventional chemical-vapor-deposited (CVD) microcrystalline Si (μc-Si) films, and the remarkable carrier transport properties would lead to effective carrier collection and resulting high quantum efficiency of FLC poly-Si solar cells.