Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 52: Nitrides: Devices

HL 52.5: Talk

Friday, March 22, 2024, 10:30–10:45, EW 015

Heterostructure design of 233 nm far-UVC LEDs with varied DPD layer thickness — •Paula Vierck¹, Jakob Höfpner¹, Marcel Schilling¹, Massimo Grigoletto², Tim Wernicke¹, and Michael Kneissl¹ — ¹Technische Universität Berlin, Institute of Solid State Physics, Berlin, Germany — ²Ferdinand Braun Institut (FBH), Berlin, Germany

Light emitting diodes (LEDs) emitting in the far ultraviolet-C (far-UVC) spectral range have applications in skin safe disinfection and gas sensing. However, their internal quantum efficiency (IQE) is still low compared to LEDs emitting in the visible spectral range. Magnesium is commonly used as the p-type dopant in AlGaN materials. It has a high ionization energy which increases even more with rising aluminum content resulting in low hole concentrations and high series resistances particularly in devices with short emission wavelengths. Instead of doping the p-AlGaN layers with magnesium, a distributed-polarization doping (DPD) layer can be used to realize a Mg-free p-side. By composition grading from an AlN-layer to an 80% AlGaN, fixed negative space charges are introduced generating free holes in the DPD-AlGaN layer which enables a highly conductive and UV-transparent p-side. In this work, a series of 233 nm LEDs was simulated comparing two different drift diffusion simulation tools while varying the DPD thickness between 50 nm and 350 nm. The impact of the DPD thickness on the devices performance and its band structure were investigated, indicating a rising IQE with decreasing DPD thickness with a maximum value of 0.28 % at 54 A/cm³ for a 50 nm thick DPD.

Keywords: AlGaN; LED; ultraviolett; DPD; External quantum efficiency