Dresden 2017 – wissenschaftliches Programm
HL 25.17: Poster
Montag, 20. März 2017, 15:00–19:00, P2-OG2
Light extraction in UVC LEDs grown on ELO AlN/sapphire templates — •Sarina Graupeter1, Martin Guttmann1, Frank Mehnke1, Christian Kuhn1, Tim Wernicke1, Mickael Lapeyrade2, Arne Knauer2, Sven Einfeldt2, Markus Weyers2, and Michael Kneissl1,2 — 1Technische Universität Berlin, Institute of Solid State Physics — 2Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin
Light emitting diodes (LEDs) in the UVC spectral range have various promising applications, e.g. gas sensing and water disinfection. However, the external quantum efficiency strongly decreases with decreasing emission wavelength. This can be partly explained by a reduced light extraction efficiency (LEE) due to an increasingly transverse magnetic polarized emission, with increasing Al content and total reflection at the AlN/sapphire interface. In this contribution, we investigate UVC LEDs using epitaxially laterally overgrown (ELO) AlN on patterned sapphire substrates, which can potentially increase the LEE due to photon redirection. The emission wavelength and the optical polarization has been varied by adjusting the aluminium content in the quantum wells, thus changing the optical polarization. Using ray tracing simulations and measurements of the far field pattern the emission has been studied in dependence of the optical polarization and the ELO geometry. Both, simulation and experiment, show that the influence of the optical polarization on the far field is negligible. However, the ELO geometry has significant influence on the far-field pattern enabling new pathways for the improvement of light extraction.