n-Type doped transparent conducting binary oxides: an overview

Abstract

This article focuses on n-type doped transparent conducting binary oxides -namely, those with the general formula M x O y :D, where M x O y is the host oxide material and D is the dopant element. Such materials are of great industrial importance in modern materials chemistry. In particular, there is a focus on the search for alternatives to indium-based materials, prompted by indium's problematic supply risk as well as a number of functional factors. The important relationship between computational study and experimental observation is explored, and an extensive comparison is made between the electrical properties of a number of the most interesting experimentally-prepared materials. In writing this article, we aim to provide both an accessible tutorial of the physical descriptions of transparent conducting oxides, and an up-to-date overview of the field, with a brief history, some key accomplishments from the past few decades, the current state of the field as well as postulation on some likely future developments.

Electron transport properties of degenerate n-type GaN prepared by pulsed sputtering

“…The sputtered polycrystalline ITO films, which are used in the TCO applications, showed the minimum resistivity of 0.15 mΩ cm. 23 However, the µ(RT) value of 100 cm 2 V 1 s 1 is much higher than that for such ITO films, which is quite advantageous for ensuring optical transparency. Although the Ge-doped samples showed slightly lower mobility because of their higher θ values compared with those of the Si-doped samples, the highest n(RT) of 5.1 × 10 20 cm 3 with a ρ(RT) of 0.20 mΩ cm was achieved by Ge doping.…”

Transparent Electrodes for Efficient Optoelectronics

“…Intrinsic dopants can also be used, with oxygen vacancies the primary example. [6] Intrinsically, the Fermi level (E F ) lies in most known TCOs close to the conduction band facilitating extrinsic n-type doping. Such doping shifts E F inside the conduction band, forming a degenerate n-type semiconductor, which also leads to further widening of the optical band gap (E g ) following the Burstein-Moss relation: ∆E g ≈ N e 2/3 .…”

“…Other reported materials with TCO properties include titanium oxide (TiO 2 ) and calcium aluminate (12CaO⋅7Al 2 O 3 ). [42,43] Conventional TCOs are binary systems, mainly polycrystalline in nature and doped with halides, group XIII, or XV elements, [6] almost always forming n-type semiconductors. Recently, multi-compound oxides (e.g., IGZO, ZTO, IZO), [44] aiming at improved mechanical properties and thermal stability due to their amorphous nature, have also been widely studied and have electrical properties that are often on par with their polycrystalline counterparts.…”

“…To this classification, we add the processing compatibility requirements for actual device fabrication and electrode integration. Because reviews on each class of transparent electrodes are available (e.g., on metal oxide electrodes for displays and thin-film transistors, [2,3] on properties of transparent conductive oxides (TCOs); [4][5][6][7] and on general properties of graphene, carbon nanotubes and metallic nanostructures [8] ), the last section presents transparent electrodes by mostly focusing on the technological development, applications, and our perspective on future developments of inorganic electrodes.…”

Polymorphism and Structural Distortions of Mixed-Metal Oxide Photocatalysts Constructed with α-U3O8 Types of Layers

“…Structural families of metal-oxides that have been commonly explored in the literature are ABO 3 pervoskites [1][2][3][4][5], layered Ruddelsden-Popper pervoskites [6][7][8], and spinel structures [9][10][11]. Metal-oxide materials can also be classified by their properties that can include superconductors [12][13][14][15], transparent conducting oxides [16][17][18][19][20], and photocatalysts [21][22][23][24][25][26]. Variations of compositions within homologous families of structures exhibit important structural transformations (i.e., structural distortions, polymorphism) which impact their optical properties (i.e., range of light absorption for photocatalysis).…”