Landolt-Börnstein - Group III Condensed Matter

2.4 Spatially resolved spectroscopy


This chapter discusses the spatially resolved spectroscopy which is generally used to investigate the diffusion length of excited species (carriers, excitons) both in bulk material and in structures of reduced dimensionality as well as ballistic and tunneling transport. For the latter group of samples spatially resolved spectroscopy is also frequently employed to separate one or a few localized states in an inhomogeneously broadened resonance. The main equipments for spatially resolved spectroscopy are various types of microscopes, pinholes or other apertures. Cathodoluminescence in a scanning electron microscope (SEM) can be also used for spatially resolved luminescence measurements. The fiber tip of a scanning near field optical microscope (SNOM) and evanescent light field is illustrated. The diffusion length of some excited species can be determined by various techniques. The diffusion or tunneling of excited species into the depth of the sample can be monitored e.g. for a superlattice or coupled quantum wells by exciting at the surface of the sample, e.g. in a cap layer and detecting the luminescence from a wider quantum well with smaller quantization energy in the depth of the sample, which can be reached by diffusion, ballistic transport or tunneling as shown schematically. Spatially resolved spectroscopy should be mentioned which is presently hardly exploited, though it is well known that a lateral confinement of the resolution results in an uncertainty.

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2.4 Spatially resolved spectroscopy
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Optical Properties. Part 1
2 Experimental methods
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Landolt-Börnstein - Group III Condensed Matter
  • C. Klingshirn
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  • C. Klingshirn
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