Regensburg 2022 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 10: Nitrides
HL 10.5: Vortrag
Montag, 5. September 2022, 16:00–16:15, H34
Drift-diffusion simulation of UVC-LEDs with varied emission wavelength — •F. Bilchenko1, A. Muhin1, M. Guttman1,2, T. Wernicke1, F. Römer3, B. Witzigmann3, and M. Kneissl1,2 — 1Technische Universität Berlin, Institute of Solid State Physics, Berlin, Germany — 2Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany — 3Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für Optoelektronik, Erlangen, Germany
The external quantum efficiency (EQE) of AlGaN-based deep ultraviolet (UVC) light emitting diodes (LEDs) decreases strongly for emission wavelengths (λ) below 240 nm by two orders of magnitude from 1% (240 nm) to 0.01% (217 nm). We showed that the light extraction efficiency (LEE) on wafer level decreases only by a factor of less than 3 from 4% (240 nm) to 1.5% (217 nm), leaving current injection efficiency (CIE) and radiative recombination efficiency (RRE) as possible major causes for the EQE decrease. In order to estimate the contribution of the CIE and RRE to the EQE we analyse measured electroluminescence characteristics by simulating an LED-series with nominally identical heterostructure but varying AlGaN composition in the active region in order to achieve λ ranging from 217 nm to 263 nm. Our results suggest that, in this wavelength range, the change in CIE contributes greatly to the decrease in EQE. For devices emitting at 263 nm and 249 nm the CIE stays roughly constant at around ∼50%, showing a significant decrease towards shorter λ, i.e. 48% at 240 nm and 2% at 217 nm. Based on these results, it appears that improvement of the CIE is paramount for achieving high-power UVC-devices.