Amorphous ZnOxNy thin films with high electron Hall mobility exceeding 200 cm2 V−1 s−1

Zinc oxynitride (ZnOxNy) has attracted much attention as an amorphous semiconductor with high electron mobility. Recent studies reported that ZnOxNy thin films grown by sputtering contained nanocrystals, which might reduce their electron mobility through grain boundary scattering. In this study, we fabricated amorphous ZnOxNy thin films on a glass substrate by a less-energetic nitrogen-plasma-assisted pulsed laser deposition (PLD) to suppress the formation of the nanocrystals. Grown by PLD under optimized conditions, these ZnOxNy thin films exhibited extremely flat surfaces with a root-mean-squared roughness (Rrms) of less than 0.3 nm. The Hall mobility of these films exceeded 200 cm2 V−1 s−1 at a critical carrier concentration of ∼1 × 1019 cm−3, which was twice as high as the reported values for sputter-deposited films. Meanwhile, the mobility of films with larger Rrms was limited to ∼160 cm2 V−1 s−1 even at the critical carrier concentration and comparable with that of the sputter-deposited ZnOxNy films. The substantial enhancement in mobility in extremely flat ZnOxNy films demonstrated that suppressing the formation of nanocrystals is the key to fabricating amorphous ZnOxNy thin films with very high mobility