High quality Al$_{0.37}$In$_{0.63}$N layers grown at low temperature (<300$^\circ$C) by radio-frequency sputtering

Abstract

High-quality Al0.37In0.63N layers have been grown by reactive radio-frequency (RF) sputtering on sapphire, glass and Si (111) at low substrate temperature (from room temperature to 300{\deg}C). Their structural, chemical and optical properties are investigated as a function of the growth temperature and type of substrate. X-ray diffraction measurements reveal that all samples have a wurtzite crystallographic structure oriented with the c-axis perpendicular to the substrate surface, without parasitic orientations. The layers preserve their Al content at 37 % for the whole range of studied growth temperature. The samples grown at low temperatures (RT and 100{\deg}C) are almost fully relaxed, showing a closely-packed columnar-like morphology with an RMS surface roughness below 3 nm. The optical band gap energy estimated for layers grown at RT and 100{\deg}C on sapphire and glass substrates is of ~2.4 eV while it red shifts to ~2.03 eV at 300{\deg}C. The feasibility of growing high crystalline quality AlInN at low growth temperature even on amorphous substrates open new application fields for this material like surface plasmon resonance sensors developed directly on optical fibers and other applications where temperature is a handicap and the material cannot be heated.