Dresden 2009 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 27: GaN: preparation and characterization I

HL 27.8: Talk

Wednesday, March 25, 2009, 11:30–11:45, BEY 81

Spatially resolved X-ray diffraction measurements on AlInN/GaN distributed Bragg reflectors — •Christoph Berger, Pascal Moser, Jürgen Bläsing, Armin Dadgar, Thomas Hempel, and Alois Krost — Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg, Deutschland

As a high-index-contrast and high-band gap material, which can be grown lattice-matched on GaN, AlInN is very promising for the fabrication of GaN-based optoelectronic devices. In vertical-cavity surface-emitting lasers (VCSELs) very high reflectivities are needed, which can be achieved by distributed Bragg reflectors (DBRs). For that purpose the layers need to have a quarter wave thickness and good crystalline quality. The DBRs were grown on GaN by metalorganic vapor phase epitaxy (MOVPE) on c-plane sapphire substrates and characterized by different X-ray diffraction (XRD) techniques, as symmetrical θ/2θ-scans, grazing-incidence in-plane diffraction (GIID) and reciprocal space mapping. Layer thicknesses and concentrations were determined and it could be shown, that the layers are grown fully strained on GaN. In θ/2θ-scans lots of satellite-peaks are observed, which implies a good periodicity and abrupt interfaces. However, spatially resolved XRD measurements revealed that the thickness ratio of the layers changes with the radial position on the wafer, which causes a shift of the corresponding optical stop band and a decrease of the maximum optical reflectivity.