Local probe techniques for luminescence studies of low-dimensional semiconductor structures

Abstract

With the rapid development of technologies for the fabrication of, as well as applications of low-dimensional structures, the demands on characterization techniques increase. Spatial resolution is especially crucial, where techniques for probing the properties of very small volumes, in the extreme case quantum structures, are essential. In this article we review the state-of-the-art in local probe techniques for studying the properties of nanostructures, concentrating on methods involving monitoring the properties related to photon emission. These techniques are sensitive enough to reveal the electronic structure of low-dimensional semiconductor structures and are, therefore, able to give detailed information about the geometrical structure, including fabrication-related inhomogeneities within an ensemble of structures. The local luminescence probe techniques discussed in this review article can be divided into four categories according to the excitation source: (i) spatially localized microphotoluminescence spectroscopy using either strong focusing or masking; (ii) near-field optical microscopy to reach below the diffraction limitation of far-field optics, by either exciting, detecting, or both exciting and detecting in the near field; (iii) cathodoluminescence using focused energetic electrons in an electron microscope; and (iv) scanning tunneling luminescence, using low-energy electrons injected or extracted from the tip of a scanning tunneling microscope.

Structural and optical properties of high quality zinc-blende/wurtzite GaAs nanowire heterostructures

“…The lifetime of the free exciton line at 1.515 eV is below 300 ps-limited by the resolution of the experimental setup, shorter than in typical bulk GaAs samples, while the lifetime of the peak at 1.46 eV is 8 ns. 34,41 The lifetime associated with these lower energy peaks is found generally between about 3 and 8 ns. This is in agreement with recent measurements in similar structures 29 and it further supports our interpretation that the lower energy peaks are due to spatially indirect recombinations in type II heterostructures.…”

Carrier transport properties in the vicinity of single self-assembled quantum dots determined by low-voltage cathodoluminescence imaging

“…Various techniques have been used to directly determine this property in low dimensional semiconductor structures. [5][6][7][8][9][10] However, for self-assembled QD structures, the exciting probe size in most cases is larger than the distance between each dot preventing from any measurement in the vicinity of a single QD.…”

Electron Microscopy Studies of Non-Local Effects’ Impact on Cathodoluminescence of Semiconductor Laser Structures

“…deep levels, carrier traps, compositional inhomogeneities), local strains, etc. [8][9][10][11] An impact of longrange or non-local effects on CL measurements has not been analyzed yet in works of other authors. It means that the nonlocal effects may have large impact on the CL signal while it is not recognized in investigations.…”