Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 51: GaN: preparation and characterization

HL 51.8: Talk

Friday, March 30, 2007, 12:45–13:00, H13

Nonpolar a-plane GaN grown on r-plane sapphire by metal-organic vapor-phase epitaxy — •Matthias Wieneke, Armin Dadgar, Jürgen Bläsing, Andre Krtschil, Thomas Hempel, and Alois Krost — Otto-von-Guericke-University Magdeburg, FNW/IEP, Postbox 4120, 39016 Magdeburg

Conventional GaN based devices grow along the [0001] c-direction. In the c-orientation, the internal spontaneous and the strain-induced piezoelectric polarization generate electric fields at heterointerfaces. These electric fields cause spatial separation of electrons and holes in quantum wells reducing the oscillator strength and red shifting the luminescence. Growing nonpolar wurtzite III-N films, as a-plane GaN for example, are a possibility to avoid polarization effects. (11-20) a-plane GaN films were grown on (1-102) r-plane sapphire by metal-organic vapor-phase epitaxy (MOVPE). By varying growth-parameters as, e.g., V-III ratio, temperature and reactor pressure several sets of samples were grown and the influence to the micro structural properties and surface morphology were studied. The grown films were investigated by high resolution X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was found that the structural properties of the films and their dependence of some growth-parameters were anisotropic in the in-plane m- and c-direction. Therefore the strain properties of a-plane GaN layers are not biaxial.