Published online by Cambridge University Press: 15 February 2011
AlxGa1-xP layers (0 ≤ x ≤ 0.7), with thicknesses of ≤ 1 μm were grown on Si (100) wafers by metal-organic molecular beam epitaxy (MOMBE) at 450 °C. Transmission electron micrographs of the single crystal films revealed that the microstructure contains stacking faults and microtwins especially near the interface as well as both threading and misfit dislocations. Hardness and elastic modulus were measured using a Nanotest 500 indenter, which can probe the film properties without influence from the substrate.
The hardness H varies linearly according to (11.8 - 2.3x) GPa. The absence of alloy hardening is due to the fact that there is no difference in atomic size of Al and Ga. The indentation modulus E/(1-v 2) decreases monotonically from 136 GPa for GaP to 129 GPa for Al0.7Ga0.3P and bows only slightly (about 2 %) below the straight line of linear interpolation.