Transient capacitance spectroscopy of defect levels in CIGS devices

The conventional DLTS, deep level transient spectroscopy, reverse-bias DLTS and Laplace transform analysis of capacitance transients have been employed for investigation of defect spectra in the bulk and at the interface of standard ZnO/CdS/Cu(In,Ga)Se-2 devices. The results are reviewed with special attention devoted to the persistent changes induced by illumination or bias voltage. In the discussion a model of mobile copper ions and shallow-deep transition of compensating donors are compared. We show, that defect relaxation model can also account for the observed phenomena, One of its consequences is a dipole layer in the interface region, consisting of positively charged interface states and negatively charged thin layer of absorber with persistently removed compensation. (C) 2000 Published by Elsevier Science S.A. All rights reserved.