No abstract

In this work, a model is developed to treat threading dislocation (TD) reduction 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 the concepts of mutual TD motion and reactions. We show that the experimentally observed slow TD reduction in GaN can be explained by low TD reaction probabilities due to TD line directions practically normal to the film surface. The behavior of screw dislocations in III-nitride films is considered and is found to strongly impact TD reduction. Dislocation reduction data in hydride vapor phase epitaxy (HVPE) grown GaN is well-described by this model. The model provides an explanation for the non-saturating TD density in thick GaN films.

Uniformly distributed precipitates have been observed by TEM in the p-type layers of laser structures. The precipitate density decreases with decreasing flow of biscyclopentadienyl-magnesium (Cp 2 Mg), which affects the hole concentrations in the p-type layers. The higher hole concentration, with the reduced precipitate density, reduces the threshold current density and improves the internal quantum efficiency because of the higher number of holes available for radiative recombination. The threshold current density is also reduced 30% from 20.8 V for lasers with a high precipitate density compared to 14.3 V for lasers with a lower precipitate density.