Structural and optical properties of InGaN/GaN nanowire heterostructures grown by PA-MBE

Abstract

The structural and optical properties of InGaN/GaN nanowire heterostructures grown by plasma-assisted molecular beam epitaxy have been studied using a combination of transmission electron microscopy, electron tomography and photoluminescence spectroscopy. It is found that, depending on In content, the strain relaxation of InGaN may be elastic or plastic. Elastic relaxation results in a pronounced radial In content gradient. Plastic relaxation is associated with the formation of misfit dislocations at the InGaN/GaN interface or with cracks in the InGaN nanowire section. In all cases, a GaN shell was formed around the InGaN core, which is assigned to differences in In and Ga diffusion mean free paths.

Comparison of the Luminous Efficiencies of Ga- and N-PolarInxGa1−xN/InFernández-Garrido1, Lähnemann2, Hauswald3 et al. 2016Phys. Rev. Applied171140View full textAdd to dashboardCite

“…Yet, numerous publications report on the luminescence of these N-polar In x Ga 1−x N disks embedded into GaN nanowires. [48][49][50][51][52] While the luminous efficiency of these structures does not seem to be even close to that of planar Ga-polar In x Ga 1−x N QWs, 49-53 they do luminesce in contrast to the planar QWs studied in the present work. Two essential differences between the In x Ga 1−x N disks inserted in GaN NWs and corresponding planar structures may contribute to this fact: first, GaN NWs are formed under N excess, 54,55 while planar QWs are grown under metal-stable conditions.…”

Single GaInP nanowire p-i-n junctions near the direct to indirect bandgap crossover point

“…23 Ordering is another possible explanation for the relatively low-energy PL, 24 but synchrotron-based x-ray diffraction measurements do not show any signs of this. 13 There may also be In-rich segments, which could be shorter than the resolution in EDS (about 5 nm), and could occur both axially, radially, as observed in GaInN NWs, 25 or at the NW edges as observed in AlInP NW shells. 26 Note, however, that we did not observe radial growth of a Ga-rich shell in TEM, 13 as previously found in MBE-grown GaInP.…”

Structure and Composition of Isolated Core-Shell(In,Ga)N/GaNRods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy

“…An important question to address is the homogeneity within large ensembles-but also of individual ensemble members themselves. Here, the analysis focus lies on the structural quality, e.g., the defects [16], the crystal phases [17][18][19], the interface quality, and the overall structural condition of complicated heterostructure objects [20][21][22][23].…”