Nano-scale luminescence characterization of individual InGaN/GaN quantum wells stacked in a microcavity using scanning transmission electron microscope cathodoluminescence

Abstract

Using cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope at liquid helium temperatures, the optical and structural properties of a 62 InGaN/GaN multiple quantum well embedded in an AlInN/GaN based microcavity are investigated at the nanometer scale. We are able to spatially resolve a spectral redshift between the individual quantum wells towards the surface. Cathodoluminescence spectral linescans allow directly visualizing the critical layer thickness in the quantum well stack resulting in the onset of plastic relaxation of the strained InGaN/GaN system.

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

“…Simultaneous to the detection of the CL‐signal, a high angle annular dark field (HAADF) electron detector is used for acquiring the STEM image. Detailed information about our STEM‐CL setup can be found elsewhere .…”

“…The intensity profile is a convolution of the excess carrier diffusion length and excitation volume described by the electron beam broadening. In our STEM‐CL experiments, the beam broadening is expected to be in the range of ∼10 nm . Hence, we assume an excess carrier diffusion length of about 30 nm in the vicinity of the intersections.…”

“…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.…”

Photon bunching reveals single-electron cathodoluminescence excitation efficiency in InGaN quantum wells

“…In CL, a high-energy electron beam in a scanning electron microscope (SEM) excites a material and generates luminescence that is collected and analyzed. CL emission gives valuable spatially resolved information about the band gap [7,8], carrier generation [9], defects [10,11], diffusion and carrier transport [12][13][14], recombination [15,16], and other optoelectronic properties of semiconductors that are used, e.g., in light-emitting diodes (LEDs) [17,18], lasers [19], solar cells [20], and more.…”

Embedded GaN nanostripes on c‐sapphire for DFB lasers with semipolar quantum wells

“…The structural and luminescence properties of individual stripes have been directly studied by a one by one correlation of the cathodoluminescence and scanning transmission electron microscopy inside a Tecnai F20 STEM. The STEM has been modified to allow spatially and spectrally resolved CL measurements at variable temperatures via cooling with liquid He and is described in more detail elsewhere . To investigate stimulated emission, resonator bars are cleaved via laser assisted cleaving() with vertical sidewalls, see Fig.…”