Process variants for Cu(In/sub 1-x/Ga/sub x/)Se/sub 2/ deposition investigated by in situ spectroscopic light scattering

We have applied in situ diffuse spectroscopic light scattering (SLS) to the three-stage deposition process of polycrystalline Cu(In/sub 1-x/Ga/sub x/)Se/sub 2/ (CIGSe) thin films. The process has been studied by systematic variation of the major process parameters of CIGSe, such as (1) substrate temperature and (2) Ga concentration. SLS signals in the wavelength range of 400/spl sim/800 nm has been used in order to derive the development of surface roughness during growth. SLS was found to be more sensitive to near-surface compositions than the conventional temperature monitoring techniques. Emergence of a Cu-rich phase at the surface before the stoichiometry point was observed by SLS. Optimum conditions for smoother ClGSe surfaces has been proposed for each process parameter.