Growth mechanism of CuZnInSe2 thin films grown by molecular beam epitaxy

CuZnInSe2 (CZIS) has potential application in solar cell for absorption layer, and give an advantage to change the band gap from CuInSe2 (1.02 eV) to ZnSe (2.67 eV). Using molecular beam epitaxy technology, the CZIS thin films were grown via CuInSe (CIS) and ZnSe base. In the case of CIS, thin films were grown on Mo-coated soda lime glass with various zinc flux. CIS was transformed into chalcopyrite and sphalerite coexisting CZIS easily but it is difficult to transform into the pure sphalerite CZIS. Zn/(Zn+In+Cu) ratio has limited to approximate 36 at% and the excess-Zn played a catalyst role. In the case of ZnSe base, which was grown on GaAs (001), various In and Cu flux defined as the T-In series and T-Cu series, respectively. There are four types of compound in the T-In series and T-Cu series, including ZnSe, InxSey, ZnIn2Se4 (ZIS) and CZIS. In the T-In series under the lowest In and Cu flux, selenium (Se) were randomly combined with cations to form the CZIS. When T-In is increased in this moment, the CZIS was transformed into ZIS. In the T-Cu series, CZIS demonstrated via In-rich ZIS (Zn(In, Cu)Se) and InxSey base ((Zn, Cu)InSe). It is chalcopyrite and sphalerite coexisting structure in the medium T-Cu region. In the high T-Cu region, it is transformed into the Zn-poor and Cu-rich CZIS. (c) 2012 Elsevier B.V. All rights reserved.