Berlin 2024 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 52: Nitrides: Devices
HL 52.9: Vortrag
Freitag, 22. März 2024, 11:45–12:00, EW 015
Influence of the MQW heterostructure variations on the efficiency of AlGaN-based DUV LEDs — •Markus A. Blonski1, Anton Muhin1, Tim Kolbe2, Sylvia Hagedorn2, Hyun Kyong Cho2, Jens Rass2, Tim Wernicke1, and Michael Kneissl1,2 — 1Technische Universität Berlin, Institute of Solid State Physics, Berlin, Germany — 2Ferdinand-Braun-Institut (FBH), Berlin, Germany
Deep ultraviolet (DUV) light emitting diodes (LEDs) with emission wavelengths shorter than 235 nm exhibit an external quantum efficiency (EQE) below 2 %. The EQE is comprised by the product of carrier injection efficiency (CIE), light extraction efficiency (LEE) and radiative recombination efficiency (RRE). In this work we investigate the RRE of epitaxially grown DUV-LEDs emitting below 235 nm using the Titkov-Dai method through a fit of the EQE. The impact of AlGaN quantum well thickness, AlGaN barrier thickness and Al molar fraction on the RRE of DUV-LEDs is investigated. To apply the Titkov-Dai method, reliable EQE measurements across a wide range of current densities from few mA/cm2 to few hundred A/cm2 are required. Accurate measurements at low currents are performed in continuous wave (cw) operation. To exclude Joule heating of the device at high currents we use pulsed electroluminescence spectroscopy with the parameters being determined by varying the pulse width, frequency and delay time between pulsed measurements and comparing them to cw measurements. At currents above 5 mA, pulsed measurements are required to suppress heating and aging of the LEDs, and for currents below 1 mA cw measurements were used to achieve lower noise levels.
Keywords: AlGaN; LED; ultraviolet; external quantum efficiency; Titkov-Dai