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

摘要

Influence of strain on the Al incorporation in Al_xGa_(l-x) N films grown on different underlayers and the properties of Al_xGa_(l-x)N/GaN two-dimensional (2D) heterostructures were investigated. The Al-containing III-nitride films and heterostructures were grown on (0001) 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_xGa_(l-x) N films from gas phase is greatly affected by the biaxial strain in the Al_xGa_(l-x) N films depending on the mismatch status between the grown Al_xGa_(l-x) N film and its underlayer. In some cases, huge mismatch between Al_xGa_(l-x) N film and the underlayer tends to result in a compositional separation in the Al_xGa_(l-x)N film. Photoluminescence (PL) measurements of Al_(0.08)Ga_(0.92)N/GaN SQW structures and absorption measurements of Al_(0.5)Ga_(0.5)N/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.