Electron channeling contrast imaging of dislocations in epitaxial GaN

Heteroepitaxial gallium nitride (GaN), typically grown on non-native substrates such as sapphire, silicon, or silicon carbide (SiC), is a key material for commercial power transistors, light-emitting diodes (LEDs), and laser diodes. Despite its widespread adoption, heteroepitaxial GaN exhibits a high density of threading dislocations (TDs) compared to other semiconductor technologies. The impact of these structural defects on the electronic and optoelectronic properties of GaN is still an area of active investigation and may prove to be a hindrance to long-term device reliability. In this work, TDs in epitaxial GaN films grown on sapphire substrates are examined via the non-destructive method of electron channeling contrast imaging (ECCI). GaN layers of three different thicknesses are analyzed using both ECCI and etch pit density measurements, confirming the expected inverse relationship between dislocation density and film thickness. Further analysis of ECCI data via dark-light contrast analysis and the g→•b→ method reveal that the dominant TD types are pureedge and mixed-type dislocations. Dislocation maps obtained via ECCI serve as a foundation for future spatially correlated studies linking individual extended defects to local electrical and optoelectronic behavior in GaN.