Multi-component transparent conducting oxides: progress in materials modelling

Abstract

Transparent conducting oxides (TCOs) play an essential role in modern optoelectronic devices through their combination of electrical conductivity and optical transparency. We review recent progress in our understanding of multi-component TCOs formed from solid-solutions of ZnO, In2O3, Ga2O3 and Al2O3, with a particular emphasis on the contributions of materials modelling, primarily based on Density Functional Theory. In particular, we highlight three major results from our work: (i) the fundamental principles governing the crystal structures of multi-component oxide structures including (In2O3)(ZnO)n, named IZO, and (In2O3)m(Ga2O3) l (ZnO)n, named IGZO; (ii) the relationship between elemental composition and optical and electrical behaviour, including valence band alignments; (iii) the high-performance of amorphous oxide semiconductors. From these advances, the challenge of the rational design of novel electroceramic materials is discussed.PACS numbers: 71.15.Mb

Conductivity in transparent oxide semiconductors

“…14(b) [195]. A detailed discussion of multi-component TCOs is beyond the scope of this review, and the interested reader should consult the review by Walsh et al [196].…”

Electronic properties of layered multicomponent wide-band-gap oxides: A combinatorial approach

“…As shown in the extensive works of Walsh et al [15] (and references therein), the coordination environment is determined by satisfying the electronic octet rule for local charge neutrality as well as the material stoichiometry. The octahedral structure in the RO 1.5 layer which maximizes the atomic separation between the negatively charged O atoms, serves as a disruptive stacking fault to the wurtzite-like AMO 2.5 layer.…”

“…The octahedral structure in the RO 1.5 layer which maximizes the atomic separation between the negatively charged O atoms, serves as a disruptive stacking fault to the wurtzite-like AMO 2.5 layer. At the same time, the A atoms, such as Al or Ga, do not have a strong preference for octahedral sites [15]. Hence, while trying to accommodate the A and M atoms and obey the electronic octet rule, changes must occur in the AMO 2.5 layer leading to the formation of five-fold trigonal bipyramid structures [15].…”

“…[1][2][3][4][5][6][7]. Multicomponent TCOs -complex oxides which contain a combination of post-transition metals, In, Zn, Ga, Cd or Sn, as well as light main-group metals such as Al or Mg -have attracted wide attention due to a possibility to manipulate the optical, electronic, and thermal properties via the chemical composition and, thus, to significantly broaden the application range of TCO materials [1,3,[6][7][8][9][10][11][12][13][14][15]. To optimize the properties of a multicomponent TCOs, it is critical to understand the role played by each constituent oxide.…”

Recent Advances in Understanding the Structure and Properties of Amorphous Oxide Semiconductors

“…Despite great technological demand for TCOs [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and extensive experimental efforts to improve the conductivity via impurity doping, [21,22] to tune the work function and carrier concentration via cation composition, [23][24][25][26][27][28] to achieve two-dimensional transport via heterointerfaces, [29] and to p-dope the oxides toward active layers of transparent electronics, [30][31][32] theoretical understanding of these fascinating materials has lagged behind significantly. The first electronic band structure of ITO was calculated in 2001; [33] the role of native defects in prototype TCOs was understood after 2002; [34][35][36][37] the properties of multi-cation TCOs were first considered in 2004 [37][38][39][40][41][42] followed by modeling of novel TCO hosts [43,44] and spin-dependent transport in transition-metal-doped TCOs; [45] the nature of the band gap in In 2 O 3 was clarified in 2008; [46] and a first highthroughput se...…”