Evidence for a Neutral Grain-Boundary Barrier in Chalcopyrites

Single grain boundaries in CuGaSe2 have been grown epitaxially. Hall measurements indicate a barrier of 30-40 meV to majority carrier transport. Nevertheless, local surface potential measurements show the absence of space charge around the grain boundary; i.e., it is neutral. Theoretical calculations [Persson and Zunger, Phys. Rev. Lett. 91, 266401 (2003)] have predicted a neutral barrier for the present Sigma3 grain boundary. Thus, we have experimentally shown the existence of a neutral grain-boundary barrier, however, smaller than theoretically predicted.