An easy approach to identify dislocation types in GaN films through selective chemical etching and atom force microscopy

摘要

Studies have revealed that different dislocation types have different influences on GaN device performance. Identification and discrimination of dislocation types in GaN films will be very helpful to understand the formation mechanism of each type of dislocation, and subsequently to work out corresponding methodologies to reduce each. In this work, two types of etched pits, inverted triangle and trapezoidal, were discovered in GaN films by AFM. Triangle ones were more quickly generated, and would transfer to the other with the increase in etching duration. Theoretical analysis from the viewpoint of strain energy of defects lets us to conclude that the former is from screw dislocation and the latter is formed by mixed dislocation. We consequently obtained the dislocation densities of each type, which agreed well with the XRD results. In summary, this work presents an easy but reliable approach to determine the type and corresponding density of dislocations in GaN.