Indium nanowires in thick (InGaN) layers as determined by x-ray analysis

Abstract

300-nm-thick InGaN layers with In concentrations up to 21% were grown by low-pressure metalorganic chemical-vapor deposition. Besides the InGaN and GaN Bragg peaks, the symmetric (0002) x-ray spectra of strain-relaxed samples show an additional signal which could be identified stemming from metallic tetragonal indium. The indium is incorporated in InGaN with its pseudohexagonal (101) plane parallel to the InGaN(0001) plane in a sixfold configuration. From the widths and intensities of the asymmetric In(211) and the symmetric In(h0h) diffraction peaks, the lateral and perpendicular crystallite sizes of the In inclusions are estimated to be ∼30 and ∼300 nm, respectively, i.e., the In is incorporated in a wire-like manner in the growth direction. In InGaN-based devices such indium wires could act as highly conducting channels detrimental for electronic and optoelectronic applications.