Films Stoichiometry Effects on the Electronic Transport Properties of Solution‐Processed Yttrium Doped Indium–Zinc Oxide Crystalline Semiconductors for Thin Film Transistor Applications

Abstract

backplanes, has fueled the development of metal oxide based semiconductors [1,2] for emerging applications. These can be either crystalline or amorphous, and combine excellent optical properties along with high electron mobility. Another advantage of metal oxides is the ease of engineering their electronic properties, by modifying their composition. The latter has resulted in the realization of multicomponent binary or ternary metal oxides aiming at the control of cationic species and ultimately the reduction of defect states and hence improved electronic transport properties and stability. To this end, several works have reported on the deposition of and metal-oxide-based thin film transistors implementing In 2 O 3 , [3][4][5][6] ZnON, [7][8][9][10] ZnSnO, [11][12][13][14][15][16] InZnO, [17][18][19][20][21][22][23][24] SnGaZnO, [25][26][27] InGaO, [28][29][30][31] ZnInSnO, [32][33][34][35] HfInZnO, [36][37][38][39] ZrInZnO, [40][41][42] and InGaZnO. [1,2,[43][44][45][46][47][48][49][50] While oxide semiconductor materials have been deposited using wellestablished vacuum-based thin films deposition methods such as pulsed laser deposition (PLD), [2,4,51,52] atomic layer deposition, [53][54][55][56][57] chemical vapor deposition, [7,58] and sputtering, [22,23,49,50] solutionbased techniques [19,47,[59][60][61][62][63][64][65][66][67][68][69][70][71][72] have also been employed over a wide range of substrate temperatures and post-deposition annealing conditions.The amorphous phase of metal oxides enables deposition of uniform films and devices over large areas. These amorphous oxide semiconductors are of a strongly ionic structure in which transfer occurs between metal and oxygen atoms; hence, they can exhibit high electron mobility, comparable to that of their crystalline counterparts, when deposited even at room temperature. [40,[61][62][63][64][65] However, voltage-bias stress instability issues, which intensify under illumination, have been reported, limiting the use of the oxide material in a number of applications. Such bias instabilities are known to be due to vacancy ionization, defect creation, and charge trapping, [66][67][68][69] in the TFT channel as well as the interface between the channel and the gate dielectric. [70] This is particularly true for InZnO where high electron mobilities have been reported, but, the increased number of defects generated strongly deteriorate the device stability. A solution to potentially stabilize the defect levels could be doping with a carrier suppressor. However, most of the carrier suppressors adversely Spray-coated crystalline InZnO x -based semiconductors are investigated as a function of [In 3+ ]:[Zn 2+ ] and their performance as TFTs semiconducting channels. More precisely, it is demonstrated that optical, structural, and electron transport properties show a high degree of sensitivity to the films' stoichiometry; that is, the [In 3+ ]:[Zn 2+ ] atomic ratio that equally determines the amorphous or crystalline structure of the film. Yttrium co-doping of InZnO x wit...

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

“…[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.…”