Synthesis of aluminium and gallium fluoroalkoxide compounds and the low pressure metal-organic chemical vapor deposition of gallium oxide films

Abstract

Aluminium and gallium fluoroalkoxide complexes of formula M(OR _f ) ₃ (HNMe ₂ ) [M=Al or Ga; R _f =CH(CF ₃ ) ₂ , CMe ₂ (CF ₃ ) or CMe(CF ₃ ) ₂ ] were prepared by reacting the corresponding metal dimethylamide complexes with fluorinated alcohols. The dimethylamine adducts reacted with 4-dimethylaminopyridine to give M(OR _f ) ₃ (4-Me ₂ Npy) [M=Al or Ga; R _f =CH(CF ₃ ) ₂ , CMe ₂ (CF ₃ ) or CMe(CF ₃ ) ₂ ]. Crystal structure analyses of Ga[OCH(CF ₃ ) ₂ ] ₃ (4-Me ₂ Npy), Ga[OCMe ₂ (CF ₃ )] ₃ (4-Me ₂ Npy) and Al[OCMe(CF ₃ ) ₂ ] ₃ (4-Me ₂ Npy) showed they have distorted tetrahedral geometries. Gallium oxide films were prepared from Ga[OCH(CF ₃ ) ₂ ] ₃ (HNMe ₂ ) and air by low-pressure chemical vapor deposition at substrate temperatures of 250-450 °C. Films deposited at 450 °C had a composition of Ga ₂ O _3.1 by backscattering analysis, an optical band gap of 4.9 eV, and were >90% transmittant in the 300-820 nm region.