Berlin 2018 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 27: Nitrides: Preparation and characterization II

HL 27.1: Vortrag

Mittwoch, 14. März 2018, 09:30–09:45, EW 203

Structural and optical characterisation of germanium doped cubic AlxGa1-xN grown by molecular beam epitaxy — •Michael Deppe¹, Fabian Tacken¹, Jürgen W. Gerlach², Dirk Reuter¹, and Donat J. As¹ — ¹Universität Paderborn, Department Physik, Warburger Straße 100, 33098 Paderborn — ²Leibniz-Institut für Oberflächenmodifizierung e.V., Permoserstraße 15, 04318 Leipzig

In the recent past, much work has been done in investigating germanium as an alternative n-type dopant in both wurtzite and zinc blende GaN. To extend the emission of nitride-based structures further into the ultraviolet spectral region, the ternary alloy Al_xGa_1−xN can be employed. The mostly used donor for wurtzite and zinc blende Al_xGa_1−xN is silicon and only little work on germanium-doping of Al_xGa_1−xN has been published. In this contribution we report on the growth and characterisation of germanium-doped cubic Al_xGa_1−xN layers with aluminium mole fractions 0 ≤ x ≤ 0.6. The aluminium mole fraction x is determined both by high resolution X-ray diffraction and energy dispersive X-ray spectroscopy. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is used to verify and quantify the incorporation of germanium into the layers. Furthermore with increasing x an increasing amount of oxygen is observed by TOF-SIMS which causes additional n-type doping. Photoluminescence (PL) spectroscopy is performed at 13 K. Up to x=0.25 the Ge-related emission exactly follows the direct band gap of cubic Al_xGa_1−xN. For higher x the PL emission sticks to a deep defect level 0.9 eV below the indirect band gap, which seems not to be related to the germanium doping.