Mobility Enhancement in P-Type SnO Thin-Film Transistors via Ni Incorporation by Co-Sputtering

Oxide semiconductors have been considered one of the most promising candidates for flexible electronics applications owing to their low process temperatures and good reliability. However, the low mobility of p-type oxide semiconductors limits the performance of flexible oxide-TFT-based CMOS technology. In this study, p-type SnO
_x
:Ni thin films were deposited by reactive rf magnetron co-sputtering, a technique compatible with the current industrial semiconductor manufacturing technology, from Sn and Ni targets. As the Ni-gun power increased, the distribution of Ni in the SnO
_x
:Ni thin film changed from a more uniform dispersion to nanoclusters, resulting in the crystalline phase transition of SnO
_x
:Ni from
$\alpha $
-SnO (110)-dominant polycrystalline to amorphous and then to
$\alpha $
-SnO (101)-dominant polycrystalline. A high-mobility inverted-staggered p-type SnO
_x
:Ni TFT was then fabricated on a glass substrate with a maximum process temperature of 225°C, which is compatible with flexible polymeric substrates. The TFT fabricated at an optimal Ni-gun power of 42 W exhibited an impressive field-effect mobility of 11 cm
²
V
⁻¹
s
⁻¹
and on current of
$35.2 ~\mu \text{A}$
per channel width-to-length ratio; these values are comparable to those of a typical n-type oxide TFT. These results should contribute toward flexible oxide-TFT-based CMOS technology.