Effect of sodium on Bridgman-grown Cu(In1-xGax)(3)Se-5 crystalline materials

Crystalline Cu(In1-xGax)(3)Se-5 ingots, corresponding to the reported order ed vacancy compound (OVC), were grown by a horizontal Bridgman method. X-ra y Lane back-reflection was performed on the as-grown surface of Cu(In1-xGax )(3)Se-5 ingots, showing the ingots to contain large single crystal regions . Hall effect measurements indicated that these materials have high electri cal resistivity. Metallic Na was, for the first time, introduced into these materials to observe the doping effect using a sealed glass ampoule. Na ca n increase the carrier concentration significantly for the CuIn3Se5 materia l (x = 0) but does not have this effect on Cu(In1-xGax)(3)Se-5 materials (x > 0). Furthermore, in the present work, contrary to the reported data for thin film material, Na did not change the conductivity type of the Cu(In1-x Gax)(3)Se-5 materials studied. Electron probe microanalysis (EPMA) showed t hat Na was detected only on the surface layer of the doped Cu(In1-xGax)(3)S e-5 samples. The electron generation mechanism in the CuIn3Se5 material due to the Na diffusion could be explained by defect generation related to Se and In sites. (C) 2001 Elsevier Science B.V. All rights reserved.