Formation by laser impact of conducting beta-Ga2O3-In2O3 solid solutions with composition gradients

Solid solutions of beta -Ga2-2xIn2xO3 (x less than or equal to 0.4) with be ta -gallia structure mere investigated by Raman spectroscopy. A continuous evolution with a linear shift of the Raman lines with increasing x was obse rved in the existence range of the solid solution (x less than or equal to 0.4). For 0.4 less than or equal to x less than or equal to 0.5, strong alt erations of the Raman spectra were observed, corresponding either to the de mixing of the solid solutions for the samples elaborated at 1400 degreesC o r to the occurrence of a new phase with kappa -alumina structure for sample s elaborated at 1550 degreesC. The in situ formation of the beta -Ga2-2x In 2xO3 compounds under laser irradiation could also be followed by Raman spec troscopy. Strong local variations of composition caused by a heterogeneous loss of indium could be detected inside the irradiated areas. In addition e lectron paramagnetic resonance revealed the existence of conduction electro ns in these areas, resulting from a slight oxygen deficiency. These gradien ts of composition induce a spatial variation of the band gap and of the pos ition of the Fermi level with respect to the conduction band so that the sy stem is equivalent to an intrinsic/n-type junction. (C) 2001 Academic Press Academic Press.