Doping Rules and Doping Prototypes in A₂BO₄ Spinel Oxides

Abstract

A2BO4 spinels constitute one of the largest groups of oxides, with potential applications in many areas of technology, including (transparent) conducting layers in solar cells. However, the electrical properties of most spinel oxides remain unknown and poorly controlled. Indeed, a significant bottleneck hindering widespread use of spinels as advanced electronic materials is the lack of understanding of the key defects rendering them as p‐type or n‐type conductors. By applying first‐principles defect calculations to a large number of spinel oxides the major trends controlling their dopability are uncovered. Anti‐site defects are the main source of electrical conductivity in these compounds. The trends in anti‐sites transition levels are systemized, revealing fundamental “doping rules”, so as to guide practical doping of these oxides. Four distinct doping types (DTs) emerge from a high‐throughput screening of a large number of spinel oxides: i) donor above acceptor, both are in the gap, i.e., both are electrically active and compensated (DT‐1), ii) acceptor above donor, and only acceptor is in the gap, i.e., only acceptor is electrically active (DT‐2), iii) acceptor above donor, and only donor is in the gap, i.e., only donor is electrically active (DT3), and iv) acceptor above donor in the gap, i.e., both donor and acceptor are electrically active, but not compensated (DT‐4). Donors and acceptors in DT‐1 materials compensate each other to a varying degree, and external doping is limited due to Fermi level pinning. Acceptors in DT‐2 and donors in DT‐3 are uncompensated and may ionize and create holes or electrons, and external doping can further enhance their concentration. Donor and acceptor in DT‐4 materials do not compensate each other, and when the net concentration of carriers is small due to deep levels, it can be enhanced by external doping.

New materials for tunable plasmonic colloidal nanocrystals

“…The extensive work of Paudel et al shows that we are still at the beginning of understanding the electrical properties of this important class of materials. 138 Here, possible future scenarios in plasmonics too could be uncovered, especially if carrier densities can be pushed up significantly. Another large class of materials is represented by perovskites, which have the general formula AMX 3 .…”

Intrinsic defects in multiferroic BiFeO3and their effect on magnetism

“…These corrections effectively remove the supercell size dependent energy of a charged system [54,55] and effectively represent the energy of an infinite crystal with a single charge (dilute limit). This approach have been used in various oxides system [56][57][58][59][60] including spinels [61] to calculate the formation enthalpy (ΔH f ) of the (charged) defect in dilute limit.…”

Understanding doping anomalies in degenerate p-type semiconductor LaCuOSe

“…The V Cu is not compensated by any other defects over the entire range of the band gap, indicating that under growth condition B, the material will be p-type in nature, with no "hole-killing" defects present. It should be noted that although "self-doping" by cation-on-cation antisites can dominate conductivity in other multi-ternary systems, 29,[84][85][86][87] in LaCuOSe both the Cu La and La Cu antisites are quite high in energy and the concentration of antisite defects in LaCuOSe is expected to be negligible under equilibrium conditions. Interestingly, the V Se is found to be an ultra deep donor, and also a negative-U type defect, possessing a +2/0 transition level at 210 meV above the VBM (or $2.5 eV below the CBM).…”