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

• Published in: Chemistry : a European journal 2021-07, Vol.27 (38), p.9791-9800
• Main Authors: Büschges, M. Isabelle, Hoffmann, Rudolf C., Regoutz, Anna, Schlueter, Christoph, Schneider, Jörg J.
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum oxide; atomic layer deposition; Atomic layer epitaxy; Chemistry; Film thickness; heterostructure; Heterostructures; Illumination; Indium; indium oxide; Indium oxides; Semiconductor devices; Thin film transistors; Thin films; thin-film transistor; Tin; Tin dioxide; Tin oxide; Tin oxides; Trimethylindium
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.202101126

Multilayered heterostructures comprising of In2O3, SnO2, and Al2O3 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 Al2O3 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 In2O3/SnO2/Al2O3 are incorporated into TFT devices, exhibiting a saturation field‐effect mobility (μsat) of 2.0 cm2 ⋅ V−1 s−1, a threshold‐voltage (Vth) of 8.6 V, a high current on/off ratio (IOn/IOff) of 1.0×107, 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). The ternary metal oxide semiconducting multilayer structure of composition [In2O3//SnO2//Al2O3] is accessible by an atomic layer deposition (ALD) approach. Oxygen deficiency in these ALD derived thin films can be effectively manipulated and controlled by adding a distinct number of alumina monolayers. Besides its semiconducting behavior, the incorporation of the alumina monolayers alters the light stability of the semiconducting multilayer thin film in a thin film transistor device under illumination in the radiation range between 300–600 nm.