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HL: Fachverband Halbleiterphysik
HL 72: Nitrides: Devices
HL 72.5: Vortrag
Donnerstag, 23. März 2017, 11:00–11:15, POT 06
Influence of the GaN:Mg contact layer on the electro-optical properties of UVB LEDs — •Norman Susilo1, Johannes Enslin1, Luca Sulmoni1, Martin Guttmann1, Ute Zeimer2, Tim Wernicke1, Markus Weyers2, and Michael Kneissl1,2 — 1Institute of Solid State Physics, Technische Universität Berlin — 2Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin
Light emitting diodes (LEDs) in the UVB spectral range (280 nm - 320 nm) are ideally suited for applications such as phototherapy and plant growth lighting. In order to improve the external quantum efficiency of UVB LEDs GaN:Mg contact layers were investigated to achieve UV-reflective and low resistance ohmic contacts. UVB LED heterostructures were grown by metal organic vapour phase epitaxy and fabricated into LED devices by standard lithography and metalization techniques. From transmission line measurements (TLM) we found that the p-contact resistivity increases rapidly with decreasing GaN:Mg thickness and exhibits a clear Schottky behaviour for layer thicknesses below 40 nm. At the same time, the emission power increases from 0.1 to 1.5 mW at 20 mA with decreasing GaN:Mg thickness. The electro-optical and the structural properties of the LEDs show that a 40 nm thick GaN:Mg cap layer is the best compromise due to the low p-contact resistivity (3.5·10−4 Ωcm2) and low absorption resulting in UVB-LEDs with external quantum efficiencies of more than 2 %, measured on-wafer.