N-type polycrystalline silicon films formed on alumina by aluminium induced crystallization and overdoping

In this work, we investigated the formation of n-type polysilicon films on alumina substrates by overdoping a p-type silicon layer obtained by aluminium induced crystallization of amorphous silicon (AIC), and subsequent epitaxy. The phosphorus doping of the AIC was carried out by thermal diffusion from a solid source. The structural quality of the n-type Si film was monitored by optical microscope and scanning electron microscope (SEM). The doping efficiency was determined by resistivity measurements and secondary ion mass spectroscopy (SIMS). The sheet resitivity changed from 2700Ω/sq to 19.6Ω/sq after thermal diffusion at 950°C for 1h, indicating the overdoping effect. The SIMS profile carried out after the high temperature epitaxy exhibits a two steps phosphorus distribution, indicating the formation of an n+n structure.