Vacancy defects in epitaxial thin filmCuGaSe2andCuInSe2

Abstract

Epitaxial thin film CuGaSe 2 and CuInSe 2 samples grown on GaAs substrates with varying [Cu]/[Ga,In] ratios were studied using positron annihilation Doppler-broadening spectroscopy and were compared to bulk crystals. We find both Cu monovacancies and Cu-Se divacancies in CuInSe 2 , whereas, in CuGaSe 2 , the only observed vacancy defect is the Cu-Se divacancy.

Electronic defects in Cu(In,Ga)Se2 : Towards a comprehensive model

“…An analysis of positron annihilation in epitaxial CuInSe 2 films based on positron lifetimes concluded Cu vacancy as the main vacancy defect in CuInSe 2 grown under Cu excess and the Cu-Se double vacancy as the main vacancy defect in Cu-poor films [89]. Similar results were obtained on epitaxial CuInSe 2 and CuGaSe 2 films based on the energy spectrum of the emitted photons [120]: in Cu-poor CuInSe 2 the double vacancy dominates, whereas in stoichiometric CuInSe 2 and CuInSe 2 grown under Cu excess the Cu vacancy dominates. In contrast, in CuGaSe 2 the double vacancy was observed for all compositions.…”

Defect identification in semiconductors with positron annihilation: Experiment and theory

“…Often for these kinds of simple systems one kind of vacancy defect dominates, making the identification with positron annihilation methods relatively straightforward, as seen in the discussions in the previous section. For multielement compounds, the definitions of stoichiometry and chemical potential are much more complicated, and it is less probable that in a given sample there would be one dominant kind of defect-this is seen, in particular, in the studies on chalcogenide-structured materials (Niki et al, 2001;Kilanski et al, 2009;Islam et al, 2011;Korhonen et al, 2012). In addition to the three possible monovacancies in such materials, the number of possible binary complexes of intrinsic defects only is strongly increased compared to simple structures (e.g., divacancies, vacancy-antisite complexes).…”

“…IV.A.3). Positron annihilation has been employed to investigate defects in these kinds of materials; see, e.g., Niki et al Guagliardo et al (2012), and Korhonen et al (2012). While the results are promising and pave the way for future studies, systematic studies are still missing.…”

Chalcopyrite compound semiconductors for thin film solar cells

“…Recently, progress has been made in determining the atomic structure of point defects: positron annihilation, which is sensitive to vacancy type defects, found the dominating vacancy defect in CuGaSe 2 to be the Cu-Se double vacancy, whereas in CuInSe 2 the double vacancy dominates only in Cu-poor material, whereas Cu-rich material contains single Cu-vacancies as the dominating vacancy type [76]. Cation related point defects have been detected by neutron diffraction in CuInSe 2 [77] and CuGaSe 2 [78]: in both cases Cu vacancies are found in Cu-poor material, in CuInSe 2 additional In Cu antisites account for the Cu deficiency, whereas in CuGaSe 2 Ga interstitial were found.…”