The growth of epitaxial aluminium on As containing compound semiconductors

The growth of epitaxial aluminium on different (1 0 0) oriented compound semiconductors grown using the molecular beam epitaxy technique have been studied. After deposition of the first complete adlayer between the aluminium and the GaAs surface as evidenced by in situ reflection high electron energy diffraction (RHEED), ex situ atomic force microscopy (AFM) images agree that subsequent aluminium deposition is via a 3D nucleated growth mode. RHEED observations during continued deposition of epitaxial aluminium indicate a 2D growth mode dominated by the (1 0 0) orientation. AFM images of the surface of the aluminium reveal that the surface morphology consists of a plateau-valley structure, while transmission electron microscopy characterisation reveals that the aluminium is a (1 0 0) oriented single crystal. For growth of epitaxial aluminium on different (1 0 0) compound semiconductors the resultant hillock-valley morphology of the aluminium is remarkably similar regardless of the underlying semiconductor. There is no apparent difference between the aluminium growth on GaAs and Al_0.6Ga_0.4As indicating that the aluminium content of the semiconductor is having no effect on the growth of the aluminium, whereas there can be a difference in the hillock widths for aluminium grown on In_0.53Al_0.47As and In_0.55Ga_0.45As. The dominant orientation that the aluminium recrystallises to, appears to be determined by the strain between the aluminium 3D nucleates and the underlying semiconductor with (1 0 0) oriented aluminium for tensile strain (growth on GaAs and AlGaAs) and (1 1 0) oriented aluminium for compressive strain (growth on InAlAs and InGaAs).