Vertical conductivity and Poole–Frenkel-ionization of Mg acceptors in AlGaN short-period superlattices with high Al mole fraction

• Published in: Applied physics letters Vol. 117; no. 25
• Main Authors: Muhin, A., Guttmann, M., Kuhn, C., Mickein, E., Aparici, J. R., Ziffer, E., Susilo, N., Sulmoni, L., Wernicke, T., Kneissl, M.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 21-12-2020
• Subjects: Aluminum; Applied physics; Current voltage characteristics; Electric fields; Field ionization; Light emitting diodes; Magnesium; Room temperature; Superlattices; Three dimensional models; Ultraviolet radiation
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0027336

Mg-doped AlGaN short-period superlattices with a high aluminum mole fraction are promising to fabricate highly efficient deep UV light emitting diodes. We present a robust and easy-to-implement experimental method for quantification of the vertical component of the anisotropic short-period superlattice conductivity based on current–voltage characteristics of devices with varying short-period superlattice thicknesses. In particular, the vertical conductivity of Al0.71Ga0.29N/Al0.65Ga0.35N:Mg short-period superlattices is investigated and found to be strongly affected by the temperature and by the applied electric field. At room temperature, the vertical conductivity varies between 5.5 × 10−7 Ω −1 cm−1 at 0.05 MV cm−1 and 6.7 × 10−5 Ω−1 cm−1 at 0.98 MV cm−1 and increases by almost two orders of magnitude when the temperature increases up to 100 °C. This behavior is in very good agreement with simulations based on a 3D-Poole–Frenkel model. In addition, the zero-field ionization energy and the inter-trap distance of the Mg acceptors in the AlGaN short-period superlattices were determined to be 510 ± 20 meV and 5.1 ± 0.3 nm, respectively.