Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 2: Nitrides: Devices

HL 2.6: Vortrag

Montag, 1. April 2019, 10:45–11:00, H31

Poole-Frenkel-ionization of acceptors in Al_0.76Ga_0.24N:Mg short-period superlattices — •A. Muhin¹, C. Kuhn¹, M. Guttmann¹, J. R. Aparici¹, L. Sulmoni¹, T. Wernicke¹, and M. Kneissl^1,2 — ¹Technische Universität Berlin, Institute of Solid State Physics, Hardenbergstraße 36, 10623 Berlin, Germany — ²Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany

For efficient light extraction in UVC light emitting diodes (LED), transparent p-doped Al_xGa_1−xN layers with x ≥ 0.6 are needed. AlGaN:Mg with such high Al mole fraction exhibits very high acceptor ionization energies leading to a very poor electrical conductivity. Nevertheless, LEDs with Al_0.81Ga_0.19N short-period superlattices (SPSL) p-side could be operated at current densities up to 4.7 kAcm⁻². This work investigates the vertical resistivity (ρ_V) of Al_0.86Ga_0.14N/Al_0.65Ga_0.35N:Mg SPSLs. The vertical resistivity of the p-AlGaN-layers was extracted from the IV-characteristics of UVC-LEDs with varied SPSL thickness. The results show that ρ_V is not constant but decreases with the electric field which reaches values up to 10⁶ Vcm⁻¹. The influence of such high electric fields on the electrical resistivity can be described by the Poole-Frenkel-effect (PFE), which leads to a field-enhanced dopant ionization. Our investigations of the field dependent ρ_V are in good agreement with the predictions made by PFE theory and provide a deeper understanding of conduction mechanisms in AlGaN:Mg SPSLs with high Al content.