HYDROGEN-INDUCED GENERATION OF ACCEPTOR-LIKE DEFECTS IN POLYCRYSTALLINE SILICON

The in situ electrical conductivity ap of undoped polycrystalline Si w as measured during exposure to monatomic H at high temperatures. Initi ally, sigma p increases due to electrons contributed by in-diffusing H donors. At long exposure times sigma p decays exponentially. Hall-eff ect data reveal that the Fermi energy shifts towards the valence band and the majority carriers change from electrons to holes indicating th e creation of acceptor states. The observed type conversion is due to the diffusion of excess H from the plasma since it does not occur duri ng exposure to other species such as oxygen. The acceptor creation is thermally activated with 1.62 eV and the accepters anneal with an acti vation energy of 2.75 eV.