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HL: Fachverband Halbleiterphysik

HL 34: Nitrides: Dots, rods, and structures

HL 34.5: Vortrag

Dienstag, 17. März 2015, 12:15–12:30, EW 201

High-reflectivity, crack-free AlN/AlGaN Bragg mirrors for deep UV micro-cavity structures — •Christoph Berger, Gordon Schmidt, Peter Veit, Armin Dadgar, Jürgen Bläsing, Jürgen Christen, and André Strittmatter — Otto-von-Guericke-Universität Magdeburg

GaN quantum dots are potential candidates to realize single photon emitters at room temperature due to their large exciton binding energy and zero-dimensional confinement potential. We have recently demonstrated narrow emission lines from single GaN quantum dots grown on AlN/sapphire templates by employing the Stranski-Krastanov regime in a MOVPE growth environment. From uPL measurements we find single emission lines with one of the smallest ever reported line width of only 450 ueV for GaN. Maximizing the emission into a distinct direction generally requires the use of mirrors which may also allow for enhanced spontaneous emission rates if such QDs were integrated inside in a resonant cavity structure. Therefore, we have developed highly reflecting, epitaxially grown distributed Bragg reflectors consisting of 50 periods of AlN/Al0.7Ga0.3N. Since these materials have a strong lattice-mismatch, in general these DBRs are subject of distinct crack-formation. Growing the DBR on a thin AlN buffer with a thickness of about 200 nm, smooth DBRs nearly free of cracks could be realized. These DBRs exhibit very high-reflectivities above 98 % at a wavelength around 270 nm. Optical and structural results from GaN quantum dots grown on top of such reflectors will be presented.