Optical properties of wurtzite/zinc-blende heterostructures in GaN nanowires

Abstract

The optical and structural properties of wurtzite GaN nanowires containing zinc-blende GaN inclusions of different thicknesses are investigated. Micro-photoluminescence spectra of single nanowires exhibit a series of narrow emission peaks with linewidth as low as 0.8 meV in the interval 3.1-3.42 eV. The peak energy blue-shifts with increasing excitation power following a $I 1/3 law due to the progressive band filling and to the screening of the internal field. The quantum confinement in these type-II crystal phase heterostructures was simulated in the framework of a one-dimensional effective mass model, accounting for the internal electrical polarization of the wurtzite GaN. The predicted transition energies are in good agreement with the energy statistics realized on more than 30 single nanowire emission spectra.

Luminescence associated with stacking faults in GaN

“…well below the ZB NBE emission at 3.27 eV. These peaks originate from ZB segments in the WZ crystal, in line with similar observations by Skromme et al [29] and Jacopin et al [33]. Taking the polarization fields of 2.5 MV/cm (P sp = −0.022 C/m 2 ) determined in [32], we have calculated the emission energies for cubic segments up to a thickness of 3 nm.…”

“…However, the linewidth obtained for the donor-bound exciton in the microcrystals investigated here amounts to only 1 meV [69] indicating that the BSF emission still suffers some form of broadening. Jacopin et al [33] reported a linewidth down to 0.8 meV on ZB/WZ quantum wells in GaN nanowires, and even lower values (< 0.5 meV) have been reported for GaAs and InP [38,61].…”

Optical properties of wurtzite GaN/AlN quantum dots grown on non-polar planes: The effect of stacking faults in the reduction of the internal electric field

“…The peak energy, however, blue-shifts clearly with increasing power for the I 1 transition, while being nearly constant for X. The overall phenomenology reported for transition I 1 is compatible with that attributed to basal stacking faults (BSFs) [14,15]. Non-polar QDs can be often crossed by BSFs which are common in a-plane AlN, as shown in TEM image of the upper inset of Fig.…”

Localization and defects in axial (In,Ga)N/GaN nanowire heterostructures investigated by spatially resolved luminescence spectroscopy

“…Furthermore, reduced growth temperatures are required for the incorporation of In. This reduced growth temperature may increase the point defect density and can facilitate the nucleation of zinc-blende (ZB) segments [9,11,33,34]. The manifestation in the luminescence spectra of both intrinsic and extrinsic point defects as well as ZB segments will be presented in the following paragraphs.…”