Charge carrier concentrations in linearly graded distributed polarization-doped layers from AlN to Al_0.8Ga_0.2N and their effect on the far-UVC LED performance

M. Schilling¹, F. Biebler¹, T. Ehlermann¹, P. Vierck¹, M. Grigoletto^1,2, J. Höpfner¹, T. Wernicke¹, and M. Kneissl^1,2

Published in:

J. Appl. Phys., vol. 139, no. 1, pp. 015702, doi:10.1063/5.0297365 (2026).

Abstract:

The effect of linearly graded AlN → Al_0.8Ga_0.2N distributed polarization-doped (DPD) layers with varying thicknesses on the net charge carrier density, output power, and external quantum efficiency (EQE) of far-ultraviolet-C light emitting diodes (far-UVC LEDs) has been investigated. Far-UVC LEDs were grown by metal-organic vapor phase epitaxy on AlN/sapphire templates with a linearly graded AlN → Al_0.8Ga_0.2N DPD layer with thicknesses between 25 and 150 nm. The net charge carrier density at the edge of the depletion region was determined via capacitance–voltage measurements increasing from (9.7 ± 0.5) × 10¹⁷ cm⁻³ for a 150 nm thick DPD layer to (2.50 ± 0.14) × 10¹⁸ cm⁻³ for a 50 nm thick AlN → Al_0.8Ga_0.2N DPD layer, which is in excellent agreement with theoretical calculations. The average on-wafer output power (EQE) at 20 mA of the far-UVC LEDs increased from 197 μW (0.19%) for LEDs with a 150 nm thick DPD layer to 314 μW (0.3%) for LEDs with a 25 nm thick DPD layer. The results show that distributed polarization doping is a promising alternative to conventional Mg doping of p-type AlGaN.

Topics:

Light emitting diodes, Capacitance voltage profiling, Quantum efficiency, Epitaxy, Doping

© 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1063/5.0297365
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