Surface structure of CuGaSe 2 (001)

Abstract

Although chalcopyrites have been used as absorber in thin film solar cells for nearly 30 years, not much is known about their surface structure, which might be an important information towards growth and interface optimization. Surface reconstructions, a general feature of semiconductor surfaces, have not been reported on Cu-III–VI 2 (001) surfaces so far. We have thus studied the chalcopyrite CuGaSe 2 (001) surface preparation by Ar + ion bombardment and annealing. The samples were grown by MOCVD on a (001) GaAs substrate on axis with a near-stoichiometric ratio Cu/Ga. The preparation was optimized so that we finally obtained a flat, well-ordered surface. The surface composition and structure was analyzed with AES, XPS, and LEED. On uncontaminated surfaces, a (1×4) reconstruction was observed with LEED which we tentatively interpret as a Se-terminated surface. XPS characterization shows a surface core level shift of −0.8 eV for the selenium surface atoms of the (1×4) reconstruction. Further investigations were carried out via AFM to characterize the surface morphology.