Berlin 2018 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 10: Nitrides: Devices

HL 10.2: Talk

Monday, March 12, 2018, 15:15–15:30, EW 203

Implementation of a GaN:Mg/GaN:Ge tunnel junction in blue vertical-cavity surface-emitting laser structures — •Christoph Berger, Silvio Neugebauer, Gordon Schmidt, Cleophace Seneza, Jürgen Bläsing, Jürgen Christen, Armin Dadgar, and André Strittmatter — Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg

Due to their unique properties GaN-based vertical-cavity surface-emitting lasers (VCSELs) are desirable for various applications. Besides the demanding realization of nitride-based microcavities with highly reflective distributed Bragg-reflectors, major challenges are the homogeneous current injection into the cavity region and the realization of a current aperture to achieve a sufficient current density in the gain region. Most commonly, current apertures are formed by selective passivation of the cavity p-side with SiO2 or SiNx and lateral current injection is accomplished by covering the aperture with an ITO-layer. In our approach the p-doped GaN is overgrown with highly doped GaN:Ge by metalorganic chemical vapor phase epitaxy. This transparent conductive nitride ensures excellent lateral current spreading, while carrier injection is enabled via tunneling at the GaN:Mg/GaN:Ge interface. Such VCSEL structures give reason to expect a significant reduction of internal losses in the cavity that are otherwise induced by the relatively high absorption coefficient of the ITO-layer. For current confinement we will address different approaches, like selective passivation of the p-GaN or selective oxidation of a buried, lattice-matched AlInN layer.