Electron-Beam-Induced Current Study of Dislocations and Leakage Sites in GaN Schottky Barrier Diodes

This work aims to clarify the electrical activities of threading dislocations and their relation with leakage sites in homoepitaxial GaN Schottky barrier diodes based on the electron-beam-induced current (EBIC) technique and transmission electron microscopy (TEM). First, the recombination activities of threading dislocations in epilayers grown on different substrates are compared by EBIC. The dislocation type is characterized based on etch pit measurements and TEM. The dislocation density and character are strongly affected by defects in the substrate. The recombination strength of dislocations is revealed to be correlated with their type. It is found that single dislocations including both edge and mixed type exhibit weak (< 5%) EBIC contrast, while dislocation clusters show strong contrast (up to 30%). Second, leakage sites in Schottky diodes are visualized by EBIC under reverse bias. There is no direct correlation between the initial leakage sites and threading dislocations; whereas, instead of dislocations, a variety of initial leakage/breakdown sites are found, including grown-in pit defects as initial breakdown sites and hillocks at the Schottky interface acting as strong leakage sites.