Effect of ultraviolet light-assisted CF4 plasma irradiation on AlGaN thin film surface

By comparing differences between characteristics of Al
_0.24
Ga
_0.76
N thin film surfaces irradiated with ultraviolet (UV) light-assisted CF
₄
plasma and with CF
₄
plasma, we clarified the effect of UV light irradiation on the surfaces. A black light lamp, which emitted photons with energies of 3.1 to 4.1 eV, was used as the UV light source. The UV light irradiation under a high gas pressure of 13 Pa changed the surface morphology as the irradiation time increased. In the case of low gas pressures of 1.3 and 6.7 Pa, the UV light irradiation did not contribute to the morphological change in the surface. The UV light irradiation also suppressed not only the amount of F atoms incorporated but also the amount of fluorides, Al(OH
_x
)F
_y
and GaF
_x
, formed in the surface. In contrast, the amount of CF
_x
incorporated in the surface was enhanced. These compositional change in the surface occurred irrespective of gas pressure.