Carrier diffusion in GaN -- a cathodoluminescence study. III: Nature of nonradiative recombination at threading dislocations

Abstract

We investigate the impact of threading dislocations with an edge component (a or a+c-type) on carrier recombination and diffusion in GaN(0001) layers close to the surface as well as in the bulk. To this end, we utilize cathodoluminescence imaging of the top surface of a GaN(0001) layer with a deeply buried (In,Ga)N quantum well. Varying the acceleration voltage of the primary electrons and comparing the signal from the layer and the quantum well enables us to probe carrier recombination at depths ranging from the close vicinity of the surface to the position of the quantum well. Our experiments are accompanied by fully three-dimensional Monte Carlo simulations of carrier drift, diffusion, and recombination in the presence of the surface, the quantum well, and the dislocation, taking into account the dislocation strain field and the resulting piezoelectric field at the dislocation outcrop. Near the surface, this field establishes an exciton dead zone around the dislocation, the extent of which is not related to the carrier diffusion length. However, reliable values of the carrier diffusion length can be extracted from the dipole-like energy shift observed in hyperspectral cathodoluminescence maps recorded around the dislocation outcrop at low acceleration voltages. For high acceleration voltages, allowing us to probe a depth where carrier recombination is unaffected by surface effects, we observe a much stronger contrast than expected from the piezoelectric field alone. This finding provides unambiguous experimental evidence for the strong nonradiative activity of edge threading dislocations in bulk GaN and hence also in buried heterostructures.

References in corpus (5)

• Dislocation contrast in cathodoluminescence and electron-beam induced current maps on GaN(0001)
• Determination of the carrier diffusion length in GaN from cathodoluminescence maps around threading dislocations: fallacies and opportunities
• Carrier diffusion in GaN -- a cathodoluminescence study. I: Temperature-dependent generation volume
• Piezoelectric field, exciton lifetime, and cathodoluminescence intensity at threading dislocations in GaN{0001}
• Carrier diffusion in GaN -- a cathodoluminescence study. II: Ambipolar vs. exciton diffusion

Cited by in corpus (4)

• Imaging non-radiative point defects buried in quantum wells using cathodoluminescence
• Carrier diffusion in GaN -- a cathodoluminescence study. I: Temperature-dependent generation volume
• Carrier diffusion in GaN -- a cathodoluminescence study. II: Ambipolar vs. exciton diffusion
• Dislocation correlations in GaN epitaxial films revealed by EBSD and XRD