Solid solutions of β-Ga 2−2x In 2x O 3 (x≤0.4) with β-gallia structure were investigated by Raman spectroscopy. A continuous evolution with a linear shift of the Raman lines with increasing x was observed in the existence range of the solid solution (x≤0.4). For 0.4≤x≤0.5, strong alterations of the Raman spectra were observed, corresponding either to the demixing of the solid solutions for the samples elaborated at 1400°C or to the occurrence of a new phase with κ-alumina structure for samples elaborated at 1550°C. The in situ formation of the β-Ga 2−2x In 2x O 3 compounds under laser irradiation could also be followed by Raman spectroscopy. Strong local variations of composition caused by a heterogeneous loss of indium could be detected inside the irradiated areas. In addition electron paramagnetic resonance revealed the existence of conduction electrons in these areas, resulting from a slight oxygen deficiency. These gradients of composition induce a spatial variation of the band gap and of the position of the Fermi level with respect to the conduction band so that the system is equivalent to an intrinsic/n-type junction.