New forms of In2Se3 and Ga2Se3 prepared by reacting InAs and GaAs substrates with selenium

Ga₂Se₃ and In₂Se₃ prepared through heterovalent substitution during thermal annealing of single-crystal gallium arsenide and indium arsenide substrates in selenium vapor in a quasi-closed system have been characterized by electron diffraction, scanning electron microscopy, and X-ray microanalysis. Cubic phases of In₂Se₃ (a ₀ = 1.1243 nm and a ₀ = 1.6890 nm) and Ga₂Se₃ (a ₀ = 1.0893 nm and a ₀ = 1.6293 nm) have been identified for the first time.