Improving the lateral homogeneity of Cu(In, Ga)Se2 layers fabricated by RF magnetron sputtering from a quaternary ceramic target

Abstract

In this study, non-layered and well-crystallized Cu(In, Ga)Se2 (CIGS) films without Se deficiency were fabricated through annealing treatment for one-step preparation of CIGS films. The as-deposited films were simply fabricated via RF magnetron sputtering of a quaternary ceramic target on the heated substrate. The films showed an anisotropic growth mode with columnar grain structure. After annealing treatment, Se deficiency presented in the as-deposited films caused by volatilization of Se during the sputtering process was compensated. Additionally, the concentrations of In and Ga remained nearly constant throughout the entire film, which means that phase separation was not found in the annealed films. Furthermore, non-layered and compact films, which help to improve the near infrared response of the devices, formed due to the recrystallization of the columnar grains. Although the roughness increased after annealing treatment, the annealed films still exhibited a relatively smooth surface. Accordingly, our results showed that annealing treatment for one-step preparation of CIGS films is an effective method to improve the lateral homogeneities of composition and morphology in the films based on quaternary sputtering.