High conductive gate leakage current channels induced by In segregation around screw- and mixed-type threading dislocations in lattice-matched In_xAl_1-xN/GaN heterostructures

A correlation between microstructures and high gate leakage current density of Schottky contacts on lattice-matched In_xAl_1-xN/GaN heterostructures has been investigated by means of current-voltage measurements, conductive atom force microscopy (C-AFM), and transmission electron microscopy (TEM) investigations. It is shown that the reverse-bias gate leakage current density of Ni/Au Schottky contacts on In_xAl_1-xN/GaN heterostructures is more than two orders of magnitude larger than that on Al_xGa_1-xN/GaN ones. C-AFM and TEM observations indicate that screw- and mixed-type threading dislocations (S/M-TDs) are efficient leakage current channels in In_xAl_1-xN barrier and In segregation is formed around S/M-TDs. It is believed that In segregation around S/M-TDs reduces local Schottky barrier height to form conductive channels and leads to high leakage current density of Schottky contacts on In_xAl_1-xN/GaN heterostructures.