Understanding the p-type defect chemistry of CuCrO2

Abstract

CuCrO 2 is the most promising Cu-based delafossite for p-type optoelectronic devices. Despite this, little is known about the p-type conduction mechanism of this material, with both Cu I /Cu II and Cr III /Cr IV hole mechanisms being proposed. In this article we examine the electronic structure, thermodynamic stability and the p-type defect chemistry of this ternary compound using density functional theory with three different approaches to the exchange and correlation; the generalized-gradient-approximation of Perdew, Burke and Ernzerhof (PBE), PBE with an additional correction for on-site Coulombic interactions (PBE + U) and the nonlocal, screened-exchange hybrid functional HSE06. The fundamental band gap of CuCrO 2 is demonstrated to be indirect in nature. Under all growth conditions, the dominant intrinsic p-type defect will be the Cu vacancy, with hole formation centered solely on the Cu sublattice. Mg doping is found to be significantly lower in energy than intrinsic defect formation, explaining the large increases in conductivity seen experimentally. Cu-rich/Cr-poor growth conditions are found to be optimal for both intrinsic and extrinsic (Mg doping) defect formation, and should be adopted to maximize performance.

Chemical bonding in copper-based transparent conducting oxides: CuMO2(M = In, Ga, Sc)

“…This analysis has been supported by calculations on the p-type chemistry of CuAlO 2 [42] and CuCrO 2 [43] which show that the thermodynamic transition levels for the copper vacancy in CuCrO 2 are much shallower than for CuAlO 2 , which is primarily mediated by the increased covalency of the Cr d states with the Cu and O states in the valence band of CuCrO 2 . These studies also highlight the vital role of the trivalent cation in any p-type conductivity.…”

Understanding doping anomalies in degenerate p-type semiconductor LaCuOSe

“…101 This is a direct consequence of the dual effect of the Cu-Se mixing at the VBM raising the VBM and ensuring a less deep acceptor level.…”

“…It has become increasingly clear, however, that all of these materials are limited by poor conductivities caused by deep acceptor levels, [29][30][31] and that the majority of Cu I based oxides …”

Raman spectra of p-type transparent semiconducting Cr2O3:Mg

“…Despite its promising properties, the processing of this doped ternary oxide remains challenging and large variations in electrical properties depending on growth conditions have been reported [8]. Part of these problems is related to the dopant distribution and the other part is due to de-phasing of the ternary oxide itself [9][10][11]. Recently we have reported on a related doped binary oxide (Cr 2 O 3 :Mg and Cr 2 O 3 :Mg,N) with similar overall properties to CuCrO 2 :Mg [12][13][14].…”