Surface characterization of AlGaN grown on Si (1 1 1) substrates

Up to 500 nm thick crack-free Al0.25Ga0.75N and Al0.32Ga0.68N epilayers have been grown on Si (1 1 1) substrates. The surface morphology of samples was investigated by an optical microscope and a scanning electron microscope (SEM). Pits and shale-like surface structure have been observed. XRD rocking curve measurements indicate the crystal quality of samples. The analyses show that the Al source flux is an important factor in growing AlGaN on Si (1 1 1). The information from the Micro-Raman spectra supported that Al atoms are gathered at nearby areas of the pits originated from the AlN/Si (1 1 1) interface in the initial stage of AlGaN growth.

► 500 nm AlGaN epilayers have been grown on Si (1 1 1) substrates.
► Pits and shale-like surface structure have been observed.
► Al source flux is a key factor in growing AlGaN on Si (1 1 1).
► Al atoms are gathered at nearby areas of the coalescence of AlN islands.