Compositional Engineering of Hf‐Doped InZnSnO Films for High‐Performance and Stability Amorphous Oxide Semiconductor Thin Film Transistors

Abstract

be employed as transparent TFTs. [13][14][15] Recently, rapid advance in transparent electronic devices for transparent TV, mobile, wearable, and even VR devices require the development of transparent TFTs and their high-performance channel layers. Moreover, AOS-based TFTs could meet the requirement of the next-generation organic light emitting diode TV, such as ultra-high frame rate, larger size, and higher resolution, due to their high mobility. [16,17] Among various metal oxide semiconductor channel materials, multicomponent metal oxide semiconductors based on the In and Zn cations matrix are considered as promising candidates for channel materials for transparent TFTs, since they have inherent merits, such as high mobility, large area uniformity from their amorphous structure, and compatibility with various processing methods. [18][19][20][21][22][23] For the realization of highperformance and highly stable oxide semiconductor-based TFTs, the control of atomic ratio in the metal oxide semiconductor channel is a key factor. For this purpose, there have been a lot of research efforts on the compositional control or doping process of the oxide semiconductor channel layer. [24][25][26][27][28][29][30][31] Olziersky et al. have reported on the role of composition of InGaZnO channel on the performance of TFT devices. [31] They referred that the InGaZnO TFTs showed improved performance and worse stability characteristics, when the In/Ga ratio is higher according to the electrical resistivity of channel films. The In cations generally play a role as a mobility enhancer, due to the spheric s orbital of the indium oxide. The TFTs with indium oxide matrix showed high mobility of 10-30 cm 2 V −1 s −1 and large current at on-state, becasue the largely overlapped s orbital of In 2 O 3 enhanced the conductivity of the electrons. [32][33][34] However, the poor stability issue of TFTs with large indium contents-channel induced by the oxygen vacancies still remain a critical drawback. [35] Several elements with high bonding strength with oxygen, such as, gallium (Ga), zirconium (Zr), hafnium (Hf), and yttrium (Y), are adopted in the indium oxide channel material as an oxygen binder and a stabilizer of the channel layer. [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] Although several elements have been employed as stabilizer in oxide semiconductor channel-based TFTs, investigation of the stabilizing element in oxide semiconductor is still lacking. In particular, The Hf-doped indium zinc tin oxide (Hf:InZnSnO) channel for high performance and stable transparent thin film transistors (TFTs) is developed by using a simultaneous cosputtering of InZnSnO and HfO 2 targets. The effects of In and Hf composition in Hf:InZnSnO channel on the performance and stability under bias stress for the Hf:InZnSnO channel-based TFTs are investigated. Herein, the In cations enhance the electrical properties, while the Hf cations reduce the oxygen vacancies in the Hf:InZnSnO channel layer. Adjusting the atomic ratio of In of the...

Tailoring of Multisource Deposition Conditions towards Required Chemical Composition of Thin Films

“…As a result, composition is often used as a default experimental variable because of its easiness to be clearly qualitatively and quantitatively expressed contrary to the other above-mentioned basic matter properties. Moreover, the thin film composition can be directly influenced by the applied deposition conditions in case of multisource depositions [ 4 , 5 ].…”

“…When considering physical vapor deposition, basically three approaches towards composition-dependent property studies exist. The first approach consists in single-source depositions of the required materials [ 5 , 10 , 11 ]. This approach, however, requires a set of source materials to cover the entire selected thin film compositional range and, therefore, it is extremely source demanding in term of the materials.…”

“…Thus, such approach is suitable when microscale characterization of the composition and selected properties are available. The last approach, usually called co-deposition, utilizes rotating substrates and multiple material sources in fixed (typically confocal) geometry [ 4 , 5 , 15 , 16 , 17 ]. This experimental setup allows obtaining large-area films with constant composition determined by applied deposition parameters.…”

“…Nonetheless, a predictive approach is rarely proposed for the determination of variable co-deposition parameters depending on the required chemical composition. These variables are often estimated a posteriori based on the experience and/or determined by feedback from experimental trials [ 4 , 5 , 15 , 16 , 17 ]. It is obvious, that this methodology is time consuming although experimental design approaches are time saving [ 18 ].…”

Low-Temperature Deposited Highly Flexible In–Zn–V–O Transparent Conductive Electrode for Perovskite Solar Cells

“…In contradiction to ITO that crystallizes rapidly at very low temperatures (<150 °C), Zn atoms have been proven to stabilize the amorphous phase of InZnO (IZO) to a high temperature of 500 °C. , Amorphous IZO thin films with a uniform and isotropic microstructure are less prone to fracture and more pliable owing to the lack of grain boundaries . Moreover, previous reports have demonstrated that the incorporation of third cations having a higher ionic valence and stronger metal-oxide bond dissociation energy than In 3+ can suppress oxygen vacancy (V O ) formation in In 2 O 3 and thus reduce the carrier concentration, which in turn tailors the optical and electrical properties of the IZO thin film as both the transmittance and resistivity are related to the carrier concentration in the thin film. , Although a number of dopants such as B, Ga, Gd, Hf, La, Sc, Si, Sr, Ta, Ti, W, Y, Zr, − etc. have been incorporated into IZO as the carrier suppresser, there are still many other candidates that have not been studied yet.…”