Modeling of threading dislocation reduction in growing GaN layers

In this work, a model is developed to treat threading dislocation (TD) redu ction in (0001) wurtzite epitaxial GaN thin films. The model is based on an approach originally proposed for (001) f.c.c. thin film growth and uses th e concepts of mutual TD motion and reactions. We show that the experimental ly observed slow TD reduction in GaN can be explained by low TD reaction pr obabilities due to TD line directions practically normal, to the film surfa ce. The behavior of screw dislocations in III-nitride films is considered a nd is found to strongly impact TD reduction. Dislocation reduction data in hydride vapor phase epitaxy (HVPE) grown GaN is well-described by this mode l. The model provides an explanation for the non-saturating TD density in t hick GaN films.