MOCVD growth of covalent and 2D GaxSey: a phase validation and characterization

Two-dimensional materials such as gallium selenide (GaSe) hold promise for optoelectronics due to their tunable bandgaps. Gallium sesquiselenide (Ga ₂ Se ₃ ), a related phase with a direct bandgap, is also suitable for integration on silicon due to its matching lattice constant. We demonstrate wafer-scale synthesis of Ga _x Se _y by metal-organic chemical vapor deposition, varying growth temperature (450–600 °C) and selenium-to-gallium ratio. To guide phase-pure growth, we construct a phase diagram. Raman spectroscopy confirms phase formation, while mass spectrometry of Di-iso-propyl selenide supports the temperature-dependent phase transition, induced by the actual selenium-to-gallium ratio on the wafer surface. Microscopy reveals distinct morphologies: Ga ₂ Se ₃ forms epitaxial films with antiphase domains on GaP/Si, while GaSe grows as faceted 〈111〉 -oriented sheets. Optical spectroscopy confirms direct transitions at 1.34 eV (Ga ₂ Se ₃ ) and 1.89 eV (GaSe). These results demonstrate controlled MOCVD growth of phase-pure Ga _x Se _y and highlight their potential for silicon-based optoelectronic integration.