Statistical investigation of dislocation induced leakage current paths in AlGaN/GaN HEMT structures on Si and the impact of growth conditions

Abstract

Threading dislocations in the AlGaN-barrier of four pairwise differently grown AlGaN/GaN high electron mobility transistor structures on Si were investigated with respect to their structural and electrical properties in direct comparison simultaneously ensuring statistical significance of the results. Portions of pure screw and mixed type dislocations were observed to serve as leakage current paths and to be clearly dependent on growth conditions like the AlN nucleation layer growth temperature. The role of impurity segregation at dislocation cores due to growth-dependent locally characteristic strain fields as for example induced by specific dislocation reactions at the AlGaN/GaN interface is discussed as the origin.