Semipolar GaInN quantum wells on pre-structured surfaces for applications in laser diodes

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In the first phase of the project "Untersuchungen zur Reduzierung der piezoelektrischen Felder in GaInN-Quantenfilmen" (Investigations of reduced piezoelectric fields in GaInN quantum wells), we have realized highly efficient semipolar light emitting diode structures on side facets of GaN stripes. Currently, as part of the second project phase, we are investigating the realization possibilities of longer wavelength laser diodes on the basis of semipolar AlGaInN structures. These structures are in particular interesting for devices like laser diodes which require stimulated emission because of the better overlap of the electron and hole wave functions. In the second phase, semipolar stripe structures with periods in the range of few hundred nanometers – suited for third order DFB gratings – and their embedding into waveguide structures have been achieved. In the third phase, we will eventually study several possible laser diode concepts: (i) Single stripe laser diodes, where a selectively deposited AlGaInN stripe directly acts as laser resonator (stripe width in the range of few micrometers); (ii) DFB-laser concept with stripe periods in the range of a few 100 nm; (iii) an arrangement of such stripes so that the light is emitted perpendicular to the surface by using well-designed interference of the stripes. A particular focus of our studies will be on the shift of the emission wavelength into the green spectral range. This requires investigations, how the In concentration in our semipolar quantum wells can be increased accordingly. In order to reach these goals, investigations about selective epitaxy of complex device structures will be done, supported by respective technology studies and various methods of locally resolved characterization.