Optical Emission of Individual GaN Nanocolumns Analyzed with High Spatial Resolution

Abstract

Selective area growth has been applied to fabricate a homogeneous array of GaN nanocolumns (NC) with high crystal quality. The structural and optical properties of single NCs have been investigated at the nanometer-scale by transmission electron microscopy (TEM) and highly spatially resolved cathodoluminescence (CL) spectroscopy performed in a scanning transmission electron microscope (STEM) at liquid helium temperatures. TEM cross-section analysis reveals excellent structural properties of the GaN NCs. Sporadically, isolated basal plane stacking faults (BSF) can be found resulting in a remarkably low BSF density in the almost entire NC ensemble. Both, defect-free NCs and NCs with few BSFs have been investigated. The low defect density within the NCs allows the characterization of individual BSFs, which is of high interest for studying their optical properties. Direct nanometer-scale correlation of the CL and STEM data clearly exhibits a spatial correlation of the emission at 360.6 nm (3.438 eV) with the location of basal plane stacking faults of type I1.

Microscopic nature of crystal phase quantum dots in ultrathin GaAs nanowires by nanoscale luminescence characterization

“…Low-temperature CL was directly applied in a STEM FEI STEM Tecnai F20 to correlate the crystalline real structure of the core-shell NW with the luminescence properties with nanometerscale resolution. In STEM mode, the focused electron beam is scanned over the NW while the emitted light is collected by a parabolic aluminum mirror and focused onto the entrance slit of the grating monochromator MonoCL4 (Gatan) [26,27]. The collected light is detected by a liquid N 2 cooled silicon charge-coupled device (CCD).…”

“…Fortunately, ultrahigh-resolution analytical capabilities combining spatially-resolved cathodoluminescence (CL) spectroscopy directly with scanning-TEM (STEM) have very recently become available to exactly identify type, microscopic nature, position and luminescence characteristics of single crystal defects at the nanoscale with resolution in the few-nm range [25]. While, so far, these capabilities have been demonstrated almost exclusively in group-III nitride based quantum nanostructures emitting in the visible to ultraviolet spectral (vis-UV) range [25][26][27][28], only few attempts have been made to explore nanoscale materials and defects emitting in the infrared [29].…”

Emission of Linearly Polarized Single Photons from Quantum Dots Contained in Nonpolar, Semipolar, and Polar Sections of Pencil-Like InGaN/GaN Nanowires

“…(c1-c4) The ~358 nm emission band originates from the GaN NW core, whereas the ~382 nm (UV), ~404 nm (violet) and ~470 nm (blue) emission bands, originate from the non-polar, semipolar and polar InGaN nanoshell sections, respectively. Strong emission intensity fluctuations are observed across the nonpolar and semipolar nanoshell regions.Direct correlation of the structural and luminescence properties on a few nanometer scale was achieved using low-temperature CL spectroscopy (T = 16 K) in a scanning transmission electron microscope (for technical details see Methods section) 31,32. Figure 3ashows the actual NW tip geometry, as resolved by HAADF-STEM.…”

Nanoscale cathodoluminescene imaging of III‐nitride‐based LEDs with semipolar quantum wells in a scanning transmission electron microscope

“…The STEM‐CL measurements are performed at an acceleration voltage of 80 keV to minimize sample damage and prevent luminescence degradation. Detailed information about the experimental setup can be found elsewhere .…”