EFFECTS OF AN ALN NUCLEATION LAYER ON MAGNETRON-SPUTTERED INDIUM NITRIDE FILMS

The effects of a thin nucleation layer of AlN on the magnetron sputtering growth of InN are investigated in comparison with films deposited onto bare sapphire surfaces. Sapphire substrates were cleaned, vacuum baked and sputter coated with a thin layer (50 nm) of AlN at 900-degrees-C. Films of InN were subsequently deposited by reactive r.f. magnetron sputtering at substrate temperatures between 50-degrees-C and 600-degrees-C. Analysis of their morphological (scanning tunneling microscopy and scanning electron microscopy), X-ray scattering (Read and precession techniques). optical absorption and electrical transport (Van der Pauw technique) properties reveals granular. epitaxial films with a high density of n-type carriers and an optical absorption edge characteristic of a highly doped semiconductor. The evolution of the physical properties of these films with increased substrate temperature is dominated by subtle changes in the granularity. This is in stark contrast to films deposited onto bare sapphire where the physical properties are dominated, at high temperature, by the formation of a large-grained morphology with significant intergranular voids.