Regensburg 2019 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 35: HL Poster II
HL 35.14: Poster
Mittwoch, 3. April 2019, 17:30–20:00, Poster E
AlGaN-based LEDs with extremely short emission wavelengths — Frank Mehnke, Luca Sulmoni, Martin Guttmann, •Tim Wernicke, and Michael Kneissl — Technische Universität Berlin, Institut für Festkörperphysik, Hardenbergstr. 36, 10623 Berlin, Germany
In this paper, we will present the development of AlGaN-based multiple quantum well (MQW) LEDs with emission between 217 nm and 239 nm applicable in gas sensing systems (e.g. NO: λ = 226 nm, NH3: λ = 217 nm). Commonly a strong decrease in emission power and external quantum efficiency is observed with decreasing emission wavelength and attributed to a reduction of carrier injection efficiency and light extraction efficiency. We discuss systematical variations of the heterostructure in order to improve the device efficiency. In order to maximize the spectral power needed for applications, the trade-off between the cut-off wavelength of the current spreading layer and its conductivity needs to be considered. Additionally, realizing ohmic contacts to AlxGa1−xN:Si with high aluminum content is extremely challenging and typically results in high operating voltages. By optimizing the four-metal electrode V/Al/Ni/Au configuration, we were able to sensibly reduce the contact resistivity of the n-contacts on Al0.9Ga0.1N:Si. Finally, we fabricated UV LEDs emitting between 239 nm and 217 nm with on-wafer measured integrated output powers ranging between 310 µW and 0.15 µW, respectively, at 20 mA in cw operation. Additionally, electroluminescence measurements under pulsed mode operation will be presented.