Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Poster 1

HL 13.19: Poster

Monday, March 26, 2007, 15:00–17:30, Poster A

Ta₂O₅/SiO₂ dielectric DBR mirrors for ZnO based micro-cavities and VCSEL structures — •Alexander Franke, Björn Diez, Thomas Hempel, Jürgen Christen, Annett Diez, Sören Heinze, and Alois Krost — Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany

For the realization of polariton lasers in ZnO and ZnO-based microcavities the fabrication of high quality Distributed Bragg Reflectors (DBRs) is essential. Epitaxial growth e.g. of MgZnO-based DBR has not been reported so far. We produce suitable DBRs operating resonantly at the bound exciton luminescence in ZnO (E = 3.36 eV) using electron beam (EB) evaporation and sputter technique. The DBRs are made of ten λ/4 multilayers of SiO₂ and Ta₂O₅ dielectric films yielding a high reflectivity of larger than 99 % and a wide stop band of about 720 meV FWHM. This assembly exhibit a high transmission at the spectral position of the E = 3.81 eV line of a HeCd laser allowing efficient optical pumping of the active region without losses. As the active region we use a 3λ/2 thick ZnO layer. The ZnO was reactively sputtered using a Zn target in an Ar and O₂ atmosphere. To further improve the quality of the active ZnO layer and in particular its surface morphology MOCVD growth of polycrystalline ZnO is used replacing the sputtering step in a second sample set.