Journal
MATERIALS
Volume 13, Issue 8, Pages -Publisher
MDPI
DOI: 10.3390/ma13081935
Keywords
oxide semiconductor; thin-film transistor; heterojunction; amorphous; device simulation; quantum confinement
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Funding
- JSPS KAKENHI [16K06309]
- Grants-in-Aid for Scientific Research [16K06309] Funding Source: KAKEN
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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 (Delta E-c) of 0.4 eV. A depth profile of background charge density indicated that a steep Delta E-c is formed even in the amorphous IGZO heterojunction interface deposited by sputtering. A field effect mobility (mu(FE)) of bottom gate structured IGZO TFTs with the heterojunction channel (hetero-IGZO TFTs) improved to 20 cm(2) V-1 s(-1), although a channel/gate insulator interface was formed by an IGZO-111 (mu(FE) = 12 cm(2) V-1 s(-1)). Device simulation analysis revealed that the improvement of mu(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 Delta E-c. Thus, we believe that heterojunction IGZO channel is an effective method to improve electrical properties of the TFTs.
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