Defect visualization of Cu(InGa)(SeS)(2) thin films using DLTS measurement

Abstract

Defect depth profiles of Cu (In1-x, Ga-x)(Se1-ySy)(2) (CIGSS) were measured as functions of pulse width and voltage via deep-level transient spectroscopy (DLTS). Four defects were observed, i.e., electron traps of similar to 0.2 eV at 140 K (E1 trap) and 0.47 eV at 300 K (E2 trap) and hole traps of similar to 0.1 eV at 100 K (H1 trap) and similar to 0.4 eV at 250 K (H2 trap). The open circuit voltage (V-OC) deteriorated when the trap densities of E2 were increased. The energy band diagrams of CIGSS were also obtained using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and DLTS data. These results showed that the valence band was lowered at higher S content. In addition, it was found that the E2 defect influenced the V-OC and could be interpreted as an extended defect. Defect depth profile images provided clear insight into the identification of defect state and density as a function of depth around the space charge region.