Investigation of the properties of In-related alloys by AFM

MOCVD grown Al1-xInxN/AlN/GaN heterostructures have been characterized by atomic force microscopy( AFM) in semi-contact and conductive mode. The surface of In-related alloys consist of grain-like structures indicating step flow and 3D-growth with TDs of density equal to ~108/cm2, the origin of which is mostly attributed to lattice mismatch between GaN and sapphire. These TDs with screw or mixed components terminate at the surface of overgrown layers as V-defects, which are six-facetted inverted pyramidal structures. Strain relaxation mechanism, formation of cracks and its propagation to the surface of the samples have been also investigated. With phase-imaging (in semi-contact AFM), we have traced sites of indium segregation in the V-defects, surface- relaxation and crack propagation in In-related alloys. These sites in V-defects and cracks were found to be highly conductive by current-AFM either due to the presence of In-segregation or due to lowering of potential barrier as a consequence of strain-relaxation. They may be the possible dominant cause of leakage current in Schottky diodes.