Capacitively coupled oxyzen plasma treatment of gallium zinc oxide

Capacitively coupled O
₂
plasma treatment effects of Ga-doped ZnO (GZO) was studied in terms of structural, optical, and electrical properties. GZO films were spin-coated onto glass and post-treated in O
₂
plasma at 0~100 W radio frequency (RF) power and 0~60 s process times in a capacitively coupled plasma system. Atomic force microscopy, X-ray diffraction, Hall measurements, UV-Vis spectroscopy, photoluminescence, and photocurrent measurement were used to characterize the influence of the O
₂
plasma post-treatment on the surface morphological, electrical, and optical properties of the GZO films. With increased RF power during O
₂
plasma post-treatment, the electrical properties of the GZO films improved significantly. The carrier concentration of the GZO films increased by a factor of approximately 52, from 5.89 × 10
¹⁷
to 3.08 × 10
¹⁹
cm
^-3
, with a 30 s O
₂
plasma exposure at 100 W RF power. The reason of electrical improvement is still under investigation for further understanding, even though it is initially attributed to the GZO films' high crystallinity, caused by the O
₂
plasma post-treatment reducing oxygen defects. The plasma treatment had little destroyed the transmittance of the GZO films. The optical band gap of the film increased with increasing RF power. An enhanced UV photocurrent was obtained within the GZO film after 30 s O
₂
plasma post-treatment at 100 W RF power, and recovery was slow. Detailed study will be discussed.