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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.