Quantum Confinement Effect in Amorphous In-Ga-Zn-O Heterojunction Channels for Thin-Film Transistors.
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ABSTRACT: Electrical and carrier transport properties in In-Ga-Zn-O thin-film transistors (IGZO TFTs) with a heterojunction channel were investigated. For the heterojunction IGZO channel, a high-In composition IGZO layer (IGZO-high-In) was deposited on a typical compositions IGZO layer (IGZO-111). From the optical properties and photoelectron yield spectroscopy measurements, the heterojunction channel was expected to have the type-II energy band diagram which possesses a conduction band offset (?Ec) of ~0.4 eV. A depth profile of background charge density indicated that a steep ?Ec is formed even in the amorphous IGZO heterojunction interface deposited by sputtering. A field effect mobility (?FE) of bottom gate structured IGZO TFTs with the heterojunction channel (hetero-IGZO TFTs) improved to ~20 cm2 V-1 s-1, although a channel/gate insulator interface was formed by an IGZO-111 (?FE = ~12 cm2 V-1 s-1). Device simulation analysis revealed that the improvement of ?FE in the hetero-IGZO TFTs was originated by a quantum confinement effect for electrons at the heterojunction interface owing to a formation of steep ?Ec. Thus, we believe that heterojunction IGZO channel is an effective method to improve electrical properties of the TFTs.
SUBMITTER: Koretomo D
PROVIDER: S-EPMC7215306 | biostudies-literature | 2020 Apr
REPOSITORIES: biostudies-literature
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