Nitrogen doping is introduced in elevated-metal metal-oxide (EMMO) thin-film transistors (TFTs) by sputtering amorphous indium gallium zinc oxide (a-IGZO) channel in Ar and N ₂ gas mixture. The electrical characteristic and reliability of TFTs under negative/positive bias illumination stress (N/PBIS) are systematically investigated on TFTs of different channel lengths (

${L}\text{s}$

). Compared with undoped TFTs, the short-channel effect (SCE) of the N-doped TFTs is significantly suppressed, the persistent photoconductivity (PPC) effect is weakened, and N/PBIS reliability is largely improved. Short- and long-channel N-doped TFTs have about the same reliability performance. X-ray photoelectron spectroscopy (XPS) analysis shows that N-doping forms Zn=N bonds in the channel and oxygen vacancies (

${V}_{O}$

) are reduced. Based on a group of TFTs with different

${L}\text{s}$

, channel mobility (

$\mu _{{\mathrm {ch}}}$

) and source–drain series resistance (

${R}_{{\mathrm {sd}}}$

) are correctly extracted. In N-doped TFTs,

$\mu _{{\mathrm {ch}}}$

has a limited decrease owing to the increase in

${R}_{{\mathrm {sd}}}$

. N-doped TFTs with different Ar/N ₂ gas-flow ratios show similar electrical and reliability performance, indicating a wide process window.

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