The preparation of gallium nitride (GaN) and gallium oxide (Ga2O3) nano-ribbons were accomplished by plasma immersion ion implantation (PIII) of nitrogen into GaAs. After PIII of nitrogen, rapid thermal annealing (RTA) was conducted on the sample. For samples annealed at 850°C for 2 minutes we observed the formation of GaN on the GaAs surface. Raman spectrum revealed a peak at 575 cm-1, which was attributed to be a blue-shifted peak (from 568 cm-1) associated with compressively strained GaN. X-ray diffraction and transmission electron microscopy (TEM) imaging were also conducted. They showed that the thickness of the region containing GaN was about 40 nm. When RTA was performed at 950°C for 2 minutes, Ga2O3 nano-ribbon was found on the GaAs sample surface. The ribbons were 0.1 to 2 μm in width, several tens of nanometers in thickness and several tens of micrometers in length. Raman spectroscopy confirmed that the ribbons are single crystalline Ga2O3. In addition, the Ga2O3 ribbons were found to possess strong visible photoluminescence.