Dresden 2014 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 100: Metamorphic structures: Bringing together incompatible materials II (Focus session with DF)
HL 100.3: Talk
Thursday, April 3, 2014, 15:45–16:00, POT 251
Characterization of strained GaN on nanometer scale by IR near field microscopy — •Fabian Gaußmann1, Stefanie Bensmann1, Jochen Wüppen1, and Thomas Taubner1,2 — 1Fraunhofer-Institut für Lasertechnik ILT, Aachen — 21. Physikalisches Institut 1A, RWTH Aachen Universität
Near-field microscopy combines the high spatial resolution of an atomic force microscopy with the depth of information that comes with spectroscopical analysis techniques. By using laser light in the mid IR range this technique is amongst others sensitive to the structure of polar materials like SiC or GaN. Regardless of the wavelength of the input laser light, the spatial resolution of these analyses is typical only a few tens of nanometer. This talk is focused on the characterization of strained gallium nitride systems. For near field analyses of GaN, laser light in the spectral range of 12 µm to 16 µm is required. This range, combined with a sufficient power density, is first covered by a novel developed tunable broadband laser system at the Fraunhofer ILT. While the two dimensional visualization of local stress fields using monochromatic laser systems is a common technique for near field analyses, we will present a method to transfer this capability to broadband laser systems. By recording single near field spectra, the optical properties and subsequent information for example about the strain, doping concentration or electron mobility can be achieved. Applied to cross-sections of layered systems, this technique gives a unique insight to the relaxation of crystal strain along the layer structure.