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

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).