Microstructure evolution of GaSe thin films grown on GaAs(100) by molecular beam epitaxy

Abstract

GaSe thin films were grown on a GaAs(100) substrate by molecular beam epitaxy. Microstructures of the thin films and interface were characterized by transmission electron microscopy. The dominant polytype formed in the GaSe thin films was a γ type, which has a 3R-rhombohedral structure with R3m space group. Predominant crystallographic orientation between the GaSe thin films and the GaAs substrate was characterized as: [1̄100]GaSe‖[011]GaAs/(0001)GaSe‖(100)GaAs. In addition, GaSe thin films with orientation of [1̄21̄0]GaSe‖[011]GaAs/(0001)GaSe‖(100)GaAs can also grow in some local areas. The interface between GaSe thin films and GaAs substrate constitutes thin intermediate layers of a vacancy ordered β-Ga2Se3, the structure of which inherits the crystallographic features of the GaAs(100) surface. Mechanisms responsible for formation of the preferable crystallographic orientation in the GaSe thin films in the initial growth stage are suggested.