SKM 2023 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 44: Nitrides: Devices
HL 44.1: Talk
Thursday, March 30, 2023, 15:00–15:15, POT 112
Highly doped GaN:Ge/GaN:Mg tunnel junctions for novel GaN-based optoelectronic devices — •Christoph Berger, Armin Dadgar, and André Strittmatter — Otto-von-Guericke-Universität Magdeburg
We report on low resistive GaN-based tunnel junctions (TJs) implemented into optoelectronic devices grown by metalorganic vapor phase epitaxy. Very high donor concentrations, which are mandatory for low-resistive TJs, are achieved by using germanium instead of commonly used silicon. Fabricated TJ-LEDs show an increased light output by more than 60 % in comparison to conventional LEDs employing indium tin oxide contacts while exhibiting a comparable differential resistance of 1.2x10−2 Ωcm2 at a current density of 100 A/cm2 and no voltage penalty by the TJ. Higher light output is attributed to a better light extraction efficiency due to V-pits formed within the GaN:Ge layer. We currently apply such tunnel-junctions in edge-emitting laser diodes as well as in vertical-cavity surface-emitting lasers. Furthermore, we will demonstrate cascaded LEDs featuring three tunnel junctions and three pn-junctions stacked on top of each other. Overgrowth of the lower LED sections affects their radiative efficiencies. We investigate different annealing concepts for acceptor activation but also the impact of annealing on the radiative recombination in the InGaN active regions.