Direct evidence of single quantum dot emission from GaN islands formed at threading dislocations using nanoscale cathodoluminescence: A source of single photons in the ultraviolet

Abstract

Intense emission from GaN islands embedded in AlN resulting from GaN/AlN quantum well growth is directly resolved by performing cathodoluminescence spectroscopy in a scanning transmission electron microscope. Line widths down to 440 μeV are measured in a wavelength region between 220 and 310 nm confirming quantum dot like electronic properties in the islands. These quantum dot states can be structurally correlated to islands of slightly enlarged thicknesses of the GaN/AlN quantum well layer preferentially formed in vicinity to dislocations. The quantum dot states exhibit single photon emission in Hanbury Brown-Twiss experiments with a clear antibunching in the second order correlation function at zero time delay.

Direct imaging of Indium-rich triangular nanoprisms self-organized formed at the edges of InGaN/GaN core-shell nanorods

“…The generated cathodoluminescence is coupled out of the microscope by a parabolically shaped mirror into the grating monochromator MonoCL4 (Gatan) and detected by a nitrogen cooled Si-CCD. Detailed information about our STEM-CL setup can be found elsewhere 21 – 23 . The STEM specimens were prepared by conventional mechanical polishing followed by Ar+ ion milling in a liquid nitrogen cooled precision ion polishing system.…”

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

“…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].…”

Nanoscale cathodoluminescence of stacking faults and partial dislocations in a‐plane GaN

“…In this study, we use nanoscale CL directly performed in a scanning transmission electron microscope (STEM‐CL) to characterize the optical properties and the real structure of SFs as well as PDs in a Si‐doped a ‐plane GaN layer simultaneously. Utilizing the higher spatial resolution of STEM‐CL , very few, up to single, SFs are addressed.…”