Regensburg 2022 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 30: Poster 2

HL 30.16: Poster

Thursday, September 8, 2022, 11:00–13:00, P3

MOVPE-grown optoelectronic devices with GaN:Mg/GaN:Ge tunnel junctions — •Christoph Berger, Armin Dadgar, Jürgen Bläsing, Gordon Schmidt, Hannes Schürmann, Peter Veit, Frank Bertram, Jürgen Christen, and André Strittmatter — Otto-von-Guericke-Universität Magdeburg, Deutschland

We report on low resistive GaN-based tunnel junctions (TJ) and TJ 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. For efficient activation of GaN:Mg, a growth process was developed that includes an in-situ activation step and overgrowth of the p-type GaN with GaN:Ge in nitrogen ambient to prevent the repassivation of the buried p-type layer. Electrical and optical characterization of the fabricated LEDs shows that GaN:Mg is efficiently activated and additional ex-situ activation is expendable. Tunnel-junction LEDs show an improved light output by approximately 20 % in comparison to conventional LEDs with semitransparent contacts and exhibit a comparable differential resistance of 1.2x10^-2 Ωcm² at a current density of 100 Acm^-2 without voltage penalty. Such tunnel-junctions were implemented in laser diode structures and were used to realize cascaded LEDs with up to three pn-junctions stacked on top of each other. We will present our latest results on the growth, the challenges and the characteristics of these sophisticated optoelectronic devices.