Dresden 2017 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 50: Nitrides: Preparation and Characterization

HL 50.8: Talk

Wednesday, March 22, 2017, 12:00–12:15, POT 251

Surface properties of p-type, n-type, and semi-insulating GaN layers on sapphire — •Aqdas Fariza, Andreas Lesnik, Silvio Neugebauer, Matthias Wieneke, Jürgen Bläsing, Hartmut Witte, Armin Dadgar, and André Strittmatter — Otto-von-Guericke University Magdeburg, Magdeburg, Germany

GaN and related heterostructures have been the subject of intensive research in recent years for optoelectronics and high power as well as high frequency devices. However, the large lattice constant mismatch between heterosubstrate and GaN epitaxial film leads to the generation of a high threading dislocation (TD) density which degrades device performance. Understanding the electrical activity of these dislocations and their surface potentials is very important to enhance the reliability of power electronics devices. Therefore, we have investigated defects in Mg-, Si-, C- and Fe-doped GaN samples with a focus on the local electronic properties of the material in the vicinity of dislocations. Dislocation densities are estimated from tilt and twist x-ray measurements using omega-scans of the (0002) reflection and in grazing incidence in-plane geometry of the (10-10) reflection. The surface topography, contact potentials and electronic charge states of dislocations are explored by performing atomic force microscopy, bias dependent electric force microscopy and scanning surface potential microscopy in tapping mode. The conductive layers exhibit a low contact potential whereas the enhanced contact potential difference for resistive GaN layers might be associated not only to the Fermi-level position but also to surface band bending and surface charges.