Strain-induced effect on the Al incorporation in AlGaN films and the properties of AlGaN/GaN heterostructures grown by metalorganic chemical vapor deposition

Abstract

Influence of strain on the Al incorporation in Al x Ga 1− x N films grown on different underlayers and the properties of Al x Ga 1− x N/GaN two-dimensional (2D) heterostructures were investigated. The Al-containing III-nitride films and heterostructures were grown on (0 0 0 1) sapphire substrates by metalorganic chemical vapor deposition using alternate supply of group III metalorganics and ammonia (NH 3). It appears that the incorporation of Al in the Al x Ga 1− x N films from gas phase is greatly affected by the biaxial strain in the Al x Ga 1− x N films depending on the mismatch status between the grown Al x Ga 1− x N film and its underlayer. In some cases, huge mismatch between Al x Ga 1− x N film and the underlayer tends to result in a compositional separation in the Al x Ga 1− x N film. Photoluminescence (PL) measurements of Al 0.08Ga 0.92N/GaN SQW structures and absorption measurements of Al 0.5Ga 0.5N/GaN SLSs and AlN/GaN SLSs reveal the same tendency of decrement in PL emission energies and reduction in absorption cut-off energies as the GaN well width in SQW and SLS increases, respectively.