Correlation of threading screw dislocation density to GaN 2-DEG mobility

A direct correlation between local threading screw dislocation densities in an aluminium gallium nitride/gallium nitride (AlGaN/GaN) heterostructure and the mobility of electrons in the two-dimensional electron gas (2-DEG) formed at the interface of that heterostructure is presented. Threading screw dislocations are directly imaged through open areas of Hall-effect test structures using electron channelling contrast imaging. The dislocation density measured for a given test structure is correlated to the mobility of the same structure. The results show a direct, negative correlation between mobility and screw/mixed dislocation density.