Vladislav Bougrov

Abstract:

We present the results on theoretical and experimental studies of threading dislocations (TDs) behavior in III-nitride layers grown in polar orientation. TDs are defects formed during epitaxial growth of layered electronic and optoelectronic materials. The effect of TDs on the functional properties of most III-nitride layers is deleterious. Optoelectronic devices fabricated from high dislocation density layers demonstrate poorer performance than those made from relatively defect-free layers. We develop a general methodology for the reduction of TD density in III-nitride layers fabricated in (0001) polar growth orientation. In such layers, the majority of TDs in as grown state are parallel to c-axis, i.e. dislocation lines are parallel to [0001] crystallographic direction. The methodology proposes to use the intentional inclination of dislocation lines from this [0001] direction by exploring various techniques: changing growth conditions, growth surface roughening and faceting, layer patterning, introduction of stressed layers, porous layer formation etc. In our studies, the reaction-kinetics approach is used to predict the behavior of TD ensemble with inclined defect lines. For example, this approach is realized when accounting for the reactions among dislocations in the ensemble. In case of III-nitride layer grown on porous template, an inclination of dislocations happens under the influence of pores. In addition, TDs can be trapping into pores. In case of the growth of the layer with faceted surface morphology, the dislocation inclination is caused by TD interaction with surface facets. The modeling results are supported with experimental data on TD density evolution in real optoelectronic device III-nitride structures.