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HL: Fachverband Halbleiterphysik

HL 33: Nitrides: Devices

HL 33.1: Vortrag

Mittwoch, 19. März 2025, 11:15–11:30, H15

Influence of barrier height variations on the efficiency of AlGaN-based 225nm LEDs — •Markus A. Blonski¹, Jakob Höpfner¹, Tim Kolbe², Sylvia Hagedorn², Hyun Kyong Cho², Jens Rass², Paula Vierck¹, Tim Wernicke¹, Michael Kneissl^1,2, and Markus Weyers² — 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 225 nm exhibit low external quantum efficiencies (EQEs). Since the AlGaN multi-quantum well (MQW) active region remains a significant limiting factor for EQE, the effects of the barrier height in the MQW region on the radiative recombination efficiency (RRE), carrier injection efficiency (CIE) and light extraction efficiency (LEE) are examined. For this, the barrier composition is varied from Al_0.82Ga_0.18N over Al_0.86Ga_0.14N to Al_0.89Ga_0.11N. The lowest barrier leads to the highest peak EQE at 0.05 % and the highest barrier to an EQE peak below 0.02 %. The RRE, CIE and LEE are determined using continuous wave and pulsed electroluminescence measurements, determination of optical polarization and Monte Carlo raytracing simulations. The analysis shows that an increase in barrier height leads to an increase in RRE and LEE and a significant decrease in CIE for an overall decrease in EQE. Drift diffusion simulations indicate a notable increase in electron spillover across the Al_0.98Ga_0.02N electron blocking layer to the p-side, attributable to a reduced band offset between barrier and electron blocking layer, reducing the CIE.

Keywords: AlGaN; UV-C; LED; Barrier height; Carrier injection