CONTROL OF CONDUCTION BEHAVIOR OF INORGANIC CRYSTALS WITH WIDE BAND GAP

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Results obatined in the present study are summarized in the following.1)Chemical design of n-type conductive and wide gap oxides. Necessary conditions for realizing high mobility of an electron in a conduction band are : A.Complex oxides of p-block cations which have an electronic configuration of (n-1)d^<10>S^0 ; B.Oxygen polyhedra of the cations constitute an edge sharing linear chain which is a highway of an electron ; C.The phase has hopefully a vacant cation site. This is expected to act as a doping site of excess cations.2)On the basis of the hypothesis MgIn_2O_4, CdGa_2O_4 and ZnGa_2O_4 with spinel structure were selected. These materials were found to be an n-type conductor and transparent for visible light because of wide band gap larger than 3.5eV.3)Finding of electron-carrier-generation by cation-implantation. Generation of electron carriers in insulating thin film of MgIn_2O_4 by Li^+-or H^+-implantation was observed. An yield of carrier electron was found to be -100%, when the flux of implanted ions was less than 10^<16>cm^<-2>.4)Some new transparent and conductive oxides with pyrochlore structure were newly found.5)In a course of study on wide gap p-type conducting oxides some S^0-S^2 mixed valence phases were found. These include Pb^<2+>-Pb^<4+>, Bi^<3+>-Bi^<5+> and Tl^+-Tl^<3+> mixed valence states.