Growth and characterization of F-doped α-Ga2O3 thin films with low electrical resistivity

F-doped alpha-Ga2O3 thin films with low electrical resistivity were epitaxially grown on c-plane alpha-Al2O3 substrates by means of mist chemical vapor deposition. The resistivity of the alpha-Ga2O3 thin films was decreased dramatically by incorporating F into alpha-Ga2O3, achieving a minimum resistivity of 6.2 x 10(-2) Omega.cm in a 1050 nm thick film grown from a precursor solution with a [F]/[Ga] ratio of 20%. Further, the carrier concentration was 1.3 x 10(19) cm(-3), and the Hall mobility was 4.6 cm(2)/Vs with the [F]/[Ga] ratio of 20% and a film thickness of 1560 nm. Secondary ion mass spectrometry revealed that the F concentration incorporated into the alpha-Ga2O3 thin film was approximately 1 x 10(20) cm(-3), and the activation ratio was approximately 10%. The higher [F]/[Ga] ratio in the precursor solution caused lower crystallinity, as demonstrated by X-ray diffraction rocking curves. For all [F]/[Ga] ratios, as the film thickness increased to approximately 1000 nm, the electrical resistivity of the thin films drastically decreased. In the thinner films, the dislocations at the interface between the alpha-Ga2O3 thin films and the alpha-Al2O3 substrates are thought to trap electrons and compensate the free carriers or deteriorate the mobility.