Performance enhancement of solution-processed InZnO thin-film transistors by Al doping and surface passivation

Abstract

Solution-processed oxide semiconductors have been considered as a potential alternative to vacuum-based ones in printable electronics. However, despite spin-coated InZnO (IZO) thin-film transistors (TFTs) have shown a relatively high mobility, the lack of carrier suppressor and the high sensitivity to oxygen and water molecules in ambient air make them potentially suffer issues of poor stability. In this work, Al is used as the third cation doping element to study the effects on the electrical, optoelectronic, and physical properties of IZO TFTs. A hydrophobic self-assembled monolayer called octadecyltrimethoxysilane is introduced as the surface passivation layer, aiming to reduce the effects from air and understand the importance of top surface conditions in solution-processed, ultra-thin oxide TFTs. Owing to the reduced trap states within the film and at the top surface enabled by the doping and passivation, the optimized TFTs show an increased current on/off ratio, a reduced drain current hysteresis, and a significantly enhanced bias stress stability, compared with the untreated ones. By combining with high-capacitance AlO x , TFTs with a low operating voltage of 1.5 V, a current on/off ratio of > 10 4 and a mobility of 4.6 cm2/(V·s) are demonstrated, suggesting the promising features for future low-cost, low-power electronics.

Improved Negative Bias Stability of Sol–Gel-Processed SnO2 Thin-Film Transistors with Vertically Controlled Carrier Concentrations

“…The electronegativity difference between Al (1.5) and O (3.5) was larger than that between Al and Sn (1.8), causing Al 3+ ions to have a stronger bond with O 2− than with Sn 4+ ions. 42 The added Al successfully decreased the number of oxygen vacancies.…”

“…The deposited Al layers were fully converted to Al 2 O 3 and the partially diffused Al 3+ functioned as an effective suppressor of VO formation. The electronegativity difference between Al (1.5) and O (3.5) was larger than that between Al and Sn (1.8), causing Al 3+ ions to have a stronger bond with O 2– than with Sn 4+ ions . The added Al successfully decreased the number of oxygen vacancies.…”

Review of Material Properties of Oxide Semiconductor Thin Films Grown by Atomic Layer Deposition for Next-Generation 3D Dynamic Random-Access Memory Devices

“…This method can solve the supercycle problem, where multilayer materials are created where the binary materials are not mixed uniformly. The elemental composition of the multicomponent thin film can be finely controlled through the injection pressure of the coinjected precursor . However, when depositing thin films using a codosing approach, unless the partial pressure of the precursor gas is perfectly homogeneous, deposition of films of uniform composition in complex nanostructures such as trenches is not possible.…”

“…The elemental composition of the multicomponent thin film can be finely controlled through the injection pressure of the coinjected precursor. 38 However, when depositing thin films using a codosing approach, unless the partial pressure of the precursor gas is perfectly homogeneous, deposition of films of uniform composition in complex nanostructures such as trenches is not possible. In the case of codosing thin films, uniform surface adsorption of both precursors is required to create a thin film with a uniform composition, so it is mainly used on spatial ALD on flat wafers.…”

IZO/ITO Double-Layered Transparent Conductive Oxide for Silicon Heterojunction Solar Cells

“…Several types of double-layered TCO were reported by several institutes, such as AZO+ITO, AZO+antimony doped tin oxide (ATO), and ZnO+ITO [11,13], so the feasibility of the SHJ solar cells with an additional TCO+ITO should be studied for the commercialization of SHJ solar cells. Zinc-doped indium oxide (IZO) has been intensively studied as transistor and TCO resulting from its high mobility and low resistivity [14][15][16][17][18]. M. Morales-Masis reported that SHJ solar cells with IZO showed a significant improvement of Jsc, which achieved an efficiency above 21.5% [14].…”