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This study shows the effects of an ultrathin Al 2 O 3 -doped ZnO (AZO) interlayer inserted between the channel layer and source/drain (S/D) electrodes on the electrical contact properties of amorphous In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs). In particular, Al 2 O 3 -doping ratio-dependent variations in electrical contacts were systemically investigated, which were modulated by adjusting the number of Al 2 O 3 injection cycles during atomic-layer-deposition (ALD) of AZO. Consequently, a-IGZO TFTs using a 1.8-nm-thick AZO interlayer (IL) with an Al 2 O 3 :ZnO sub-cycle ratio of 2:8 showed the lowest specific contact resistivity of (4.2 ± 7.3) × 10 -7 Ω·cm 2 . This value is three orders of magnitude lower than that of devices without the AZO IL. This substantial improvement could be attributed to the IL's high electron concentration of 1.9 × 10 18 /cm 3 , which greatly lowered the effective Schottky barrier height between IGZO and the S/D electrodes. This enhanced electrical contact led to a field-effect mobility increase from 38.8 ± 0.8 to 45. 3 ± 0.6 cm 2 /Vs.
Jeong et al. (Mon,) studied this question.