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HL: Fachverband Halbleiterphysik

HL 65: GaN-based Devices

HL 65.2: Vortrag

Freitag, 26. März 2010, 10:30–10:45, H15

Anisotropy in semipolar InGaN laser diodes: Consequences for resonator design and facet formation — •Jens Rass¹, Tim Wernicke², Wilfred John², Sven Einfeldt², Patrick Vogt¹, Markus Weyers², and Michael Kneissl^1,2 — ¹Technische Universitaet Berlin, Institute of Solid State Physics, Hardenbergstrasse 36, 10623 Berlin — ²Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin

For InAlGaN-based light emitting devices on nonpolar and semipolar substrate orientations the polarization fields can be reduced. Birefringence and gain anisotropy influence the optical modes of semipolar separate confinement hetero structures. We have investigated the threshold for amplified spontaneous emission and the optical polarization state of the eigenmodes for laser resonators with different orientations on various semipolar and nonpolar substrates. We found that semipolar resonators along the projection of the c-axis onto the surface have a lower threshold and the light is TE-polarized. Nonpolar resonators perpendicular to the c-axis on the other hand have elevated thresholds and hence a lower gain as well as a tilted linear optical polarization with the electric field nearly parallel to the c-axis of the crystal.

In order to obtain devices with low threshold and maximum performance, laser resonators on semipolar substrates have to be oriented along the semipolar orientation, posing a challenge for the fabrication of laser facets. Technologies such as laser assisted cleaving, chemical dry etching and wet chemical post processing are presented and their suitability for the generation of smooth vertical facets is discussed.