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The authors have applied positron annihilation spectroscopy to study the effect of different growth conditions on vacancy formation in In- and N-polar InN grown by plasma-assisted molecular beam epitaxy. The results suggest that the structural quality of the material and limited diffusion of surface adatoms during growth dictate the In vacancy formation in low electron-density undoped epitaxial InN, while growth conditions and thermodynamics have a less important role, contrary to what is observed in, e.g., GaN. Furthermore, the results imply that in high quality InN, the electron mobility is likely limited not by ionized point defect scattering, but rather by threading dislocations. [ABSTRACT FROM AUTHOR]

The surface electron accumulation layer, surface structure, and surface chemical states of a-plane (nonpolar) and c-plane (polar) InN epitaxial films were investigated. Electrical measurements indicated electron accumulation layers on the surface of both the InN films. Angle-resolved x-ray photoelectron spectroscopy (XPS) measurements indicated a strong band bending at both surfaces, thus confirming the surface electron accumulation. Further XPS analysis of the near-surface chemical states indicated an In adlayer at the surface of c-plane InN and an oxygen adsorbed layer on the a-plane InN. These results suggest different ad-layers to cause the surface electron accumulation on c-plane and a-plane InN. [ABSTRACT FROM AUTHOR]

The authors report on InGaN microcavity light-emitting diodes with an effective thickness of ∼450 nm at the emission wavelength of ∼415 nm. The starting material for the flip-chip laser lift-off device is a structure with an active region embedding six InGaN/GaN quantum wells, ∼60-nm-thick AlGaN, and a GaN template grown on a c-plane sapphire substrate. High-precision control of the final microcavity thickness was facilitated by SF6-based selective inductively coupled plasma etching on the flipped material with an etch rate of >=5:1 for GaN:AlxGa1-xN, where x>=0.15. Pronounced microcavity effects were observed by angular measurements, in agreement with the theoretical cavity-mode dispersion characteristics. [ABSTRACT FROM AUTHOR]