Regensburg 2016 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 50: Gallium Nitride: Fabrication and Characterization
HL 50.12: Vortrag
Mittwoch, 9. März 2016, 12:45–13:00, H17
Structural characterization and scanning surface potential microscopy (SSPM) of C-doped GaN layers on Sapphire — •Aqdas Fariza, Hartmut Witte, Andreas Lesnik, Jürgen Bläsing, Peter Veit, Armin Dadgar, and Andre Strittmatter — Institute of Experimental Physics, Otto von Guericke University Magdeburg, Magdeburg, Germany
We have compared undoped and C-doped GaN samples with a focus on electrical properties of the material in the vicinity of dislocations. Photoluminescence measurements showed an increase of blue and yellow band emission intensities with increasing carbon concentrations which points to an enhanced incorporation of deep defects. Dislocation densities are estimated from tilt and twist x-ray measurements using omega-scans for the (0002) reflection and grazing incidence in-plane geometry for the (10-10) reflection. Values of skew and edge type dislocation densities are obtained in the range of 108 cm−2 and 109 cm−2, respectively, independent of the carbon content. The type of dislocations in the GaN layer is determined from TEM images. The surface topography and electronic charge state of dislocations are explored by performing atomic force microscopy and scanning surface potential measurements in tapping mode. The charging state of dislocations in unintentionally doped samples is either neutral or negative whereas positively charged surface depressions are also found in highly carbon doped samples.