Atomic Layer Deposition of Ternary Indium/Tin/Aluminum Oxide Thin Films, Their Characterization and Transistor Performance under Illumination

Chemistry - a European journal 27(38), 9791-9800 (2021). doi:10.1002/chem.202101126
Multilayered heterostructures comprising of In$_2$O$_3$, SnO$_2$, and Al$_2$O$_3$ were studied for their application in thin-film transistors (TFT). The compositional influence of tin oxide on the properties of the thin-film, as well as on the TFT characteristics is investigated. The heterostructures are fabricated by atomic layer deposition (ALD) at 200 °C, employing trimethylindium (TMI), tetrakis(dimethylamino)tin (TDMASn), trimethylaluminum (TMA), and water as precursors. After post-deposition annealing at 400 °C the thin-films are found to be amorphous, however, they show a discrete layer structure of the individual oxides of uniform film thickness and high optical transparency in the visible region. Incorporation of only two monolayers of Al$_2$O$_3$ in the active semiconducting layer the formation of oxygen vacancies can be effectively suppressed, resulting in an improved semiconducting and switching behavior. The heterostacks comprising of In$_2$O$_3$/SnO$_2$/Al$_2$O$_3$ are incorporated into TFT devices, exhibiting a saturation field-effect mobility ($μ_{sat}$) of 2.0 cm$^2$⋅ V$^{−1}$ s$^{−1}$, a threshold-voltage (V$_{th}$) of 8.6 V, a high current on/off ratio (I$_{On}$/I$_{Off}$) of 1.0×10$^7$, and a subthreshold swing (SS) of 485 mV ⋅ dec$^{−1}$. The stability of the TFT under illumination is also altered to a significant extent. A change in the transfer characteristic towards conductive behavior is evident when illuminated with light of an energy of 3.1 eV (400 nm).
Published by Wiley-VCH, Weinheim