Abstract

Amorphous silicon zinc tin oxide (a-SZTO) thin-film transistors (TFTs) were fabricated and systematically investigated by varying the oxygen flow parameter (OFP) during channel deposition and the metal capping (MC) width on the device structure. The a-SZTO active layer was deposited by RF sputtering, while Ti/Al was used as the source/drain electrode and metal capping layer. The effects of OFP and MC width on the electrical performance of the TFTs were analyzed through current-voltage measurements, including field-effect mobility (µFE), threshold voltage (Vth), subthreshold swing (SS) and total trap density (NT). For uncapped devices, increasing the OFP from 0 to 10 sccm reduced µFE from 14.53 to 8.85 cm2/Vs and shifted Vth from 3.68 to 7.31 V, while SS improved from 0.78 to 0.66 V/decade and NT decreased from 3.41 to 2.09 × 1012 cm-2eV-1. These results indicate that higher oxygen incorporation suppresses oxygen-vacancy-related donor states and reduces trap density but also lowers the free carrier concentration in the channel. In contrast, the introduction of the Ti/Al metal capping layer increased µFE and shifted Vth in the negative direction for all OFP conditions, confirming enhanced electron injection from the capping layer into the a-SZTO channel. At an OFP of 10 sccm, µFE increased from 8.85 to 11.02 cm2/Vs and Vth shifted from 7.31 to -1.18 V as the MC width increased from 0 to 40 µm. The transfer-characteristic trends were also consistent with the output characteristics, further verifying that OFP and MC width strongly influence carrier concentration and channel conductivity.

Keywords

Amorphouse Oxide, SZTO, TFT, Thin-Film Transistor, Metal Capping Layer,

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References

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