Role of order and disorder in covalent semiconductors and ionic oxides used to produce thin film transistors

Investigation of solution-processed amorphous SrInZnO thin film transistors

“…These advantages of TAOS over conventional hydrogenated amorphous Si are derived from the electrical transport between an ionic oxide semiconductor and a covalent semiconductor. Unlike the covalent semiconductor, which is strongly affected by the angular distribution of the sp 3 orbitals in the amorphous phase, an ionic oxide semiconductor is little affected by the angular distribution of its 2p orbitals because of the spherically extended ns (n Z5) orbitals of the post-transition metal, which allows for overlap with the neighboring metal ns orbital [1][2][3][4]. Because of this unique carrier transport mechanism, some ZnO-based materials, including post-transition metal cations (In 3 + or Sn 4 + ) such as InZnO (IZO) [5] and ZnSnO (ZTO) [6], have been investigated.…”

“…Many studies on transparent amorphous oxide semiconductors (TAOS) have been reported, especially for application in large-area flat panel displays, because they satisfy requirements for high mobility, high transparency, excellent electrical stability, and large-scale deposition capability with good uniformity [1][2][3][4]. These advantages of TAOS over conventional hydrogenated amorphous Si are derived from the electrical transport between an ionic oxide semiconductor and a covalent semiconductor.…”

“…Because of this unique carrier transport mechanism, some ZnO-based materials, including post-transition metal cations (In 3 + or Sn 4 + ) such as InZnO (IZO) [5] and ZnSnO (ZTO) [6], have been investigated. To achieve additional controllability of the thin film transistor (TFT) based on this concept, there have been numerous attempts to include a third carrier suppressor since the use of Ga was reported by Hosono et al [1][2][3][7][8][9][10][11][12]. SrO is a known electrical insulator [13][14][15][16] with a bandgap of 5.7 eV [13], an electronegativity of 0.95, and a dielectric constant of 3.2 [17].…”

Electrical properties of ZnO-based bottom-gate thin film transistors fabricated by using radio frequency magnetron sputtering

“…For these reason, several groups have focused on ZnO TFTs for use in active matrix liquid crystal displays (AMLCD) and improvements in device performance. The majority of these studies have been based on various substrates, gate and gate insulator layers in order to find a suitable device structure for ZnO TFTs that meets specific application requirements and to enhance device performance [13][14][15][16][17]. There are several technological issues to be solved for ZnO TFTs to be used in practical application.…”

Oxide semiconductors: Order within the disorder

“…When comparing the electronic performance of the oxides above mentioned with the covalent semiconductors, we observe huge differences, either concerning the doping effect or the role of disorder and order on the materials and devices' properties [48,49]. In fact, in covalent semiconductors, the electronic doping effect is mainly related to the substitution of atoms in a matrix (host) by an impurity, which may have a deficit or an excess of valence electrons relatively to the host atoms, leading to a negative or positive charge impurity, to each is connected the existence of an excess of free holes (p-type), or of free electrons (n-type), respectively [50].…”