Characterization of MOVPE-grown InN layers on α-Al2O3 and GaAs substrates

Heteroepitaxial layers of InN grown on alpha-Al2O3(0 0 0 1): GaAs(1 1 1)B and GaAs(1 0 0) substrates using metalorganic vapor-phase epitaxy (MOVPE) have been characterized comparatively. A single-crystalline InN with wurtzite structure is grown on alpha-Al2O3(0 0 0 1) and GaAs(1 1 1)B substrates, while zincblende InN is grown with a small fraction of wurtzite phase on GaAs(1 0 0) substrate. Surface morphology is the best for InN grown on GaAs(1 1 1)B. Electrical property of InN films on alpha-Al2O3(0 0 0 1) is markedly dependent on NH3/TMI molar ratio during the growth. The growth at the atmospheric pressure with a higher NH3/TMI molar ratio is found to be effective to achieve excellent electrical properties (n similar to 5 x 10(19) cm(-3), mu(H) similar to 300 cm(2)/V s). InN films grown on GaAs(1 1 1)B have a higher carrier density and a lower mobility even when they are grown under the optimized conditions, although they have an excellent surface morphology. (C) 1998 Elsevier Science B.V. All rights reserved.