Native point defects in CuIn$_{1-x}$Ga$_x$Se$_{2}$: hybrid density functional calculations predict origin of p- and n-type conductivity

Jonas Bekaert; Rolando Saniz; Bart Partoens; Dirk Lamoen

doi:10.1039/C4CP02870H

paper

Native point defects in CuIn $_{1 - x}$ Ga $_{x}$ Se $_{2}$ : hybrid density functional calculations predict origin of p- and n-type conductivity

arXiv:1407.0210 · doi:10.1039/C4CP02870H

Abstract

We have performed a first-principles study of the p- and n-type conductivity in CuIn $_{1 - x}$ Ga $_{x}$ Se $_{2}$ due to native point defects, based on the HSE06 hybrid functional. Band alignment shows that the band gap becomes larger with $x$ due to the increasing conduction band minimum, rendering it hard to establish n-type conductivity in CuGaSe $_{2}$ . From the defect formation energies, we find that In/Ga $_{Cu}$ is a shallow donor, while V $_{Cu}$ , V $_{In / Ga}$ and Cu $_{In / Ga}$ act as shallow acceptors. Using total charge neutrality of ionized defects and intrinsic charge carriers to determine the Fermi level, we show that under In-rich growth conditions In $_{Cu}$ causes strongly n-type conductivity in CuInSe $_{2}$ . Under In-poor growth conditions the conductivity type in CuInSe $_{2}$ alters to p-type and compensation of the acceptors by In $_{Cu}$ reduces, as observed in photoluminescence experiments. In CuGaSe $_{2}$ , the native acceptors pin the Fermi level far away from the conduction band minimum, thus inhibiting n-type conductivity. On the other hand, CuGaSe $_{2}$ shows strong p-type conductivity under a wide range of Ga-poor growth conditions. Maximal p-type conductivity in CuIn $_{1 - x}$ Ga $_{x}$ Se $_{2}$ is reached under In/Ga-poor growth conditions, in agreement with charge concentration measurements on samples with In/Ga-poor stoichiometry, and is primarily due to the dominant acceptor Cu $_{In / Ga}$ .

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Abstract

Cited by in corpus (1)

Native point defects in CuIn $_{1 - x}$ Ga $_{x}$ Se $_{2}$ : hybrid density functional calculations predict origin of p- and n-type conductivity