Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 56: Non- and Semi-polar Group-III-Nitrides
HL 56.4: Vortrag
Donnerstag, 25. März 2010, 14:45–15:00, H15
Surface morphology of homoepitaxial GaN grown on non- and semipolar GaN substrates — •Tim Wernicke1, Simon Ploch2, Veit Hoffmann1, Jens Rass2, Carsten Netzel1, Lukas Schade3, Ulrich Schwarz3, Arne Knauer1, Markus Weyers1, and Michael Kneissl1,2 — 1FBH Berlin, Germany — 2Institute of Solid State Physics, TU Berlin, Germany — 3IAF, Freiburg, Germany
Recently a number of groups have reported laser diodes in the green spectral range on semi- and nonpolar GaN. Nevertheless the growth process on semipolar surfaces is not well understood. In this study 3.5 µ m thick MOVPE grown GaN layers on bulk m-plane, (1122), (1012), and (1011) GaN substrates were investigated. XRD rocking curves exhibit a FWHM of less than 150", indicating excellent crystalline quality. But the surface morphology exhibits hillocks with a height of 1 µ m and lateral extension of 150 µ m in many cases. Depending on the substrate orientation and the growth temperature different hillock shapes were observed. Morphology and luminescence data point to threading dislocations as formation sources. In QWs the hillock structure is reproduced in the emission intensity and wavelength distribution on (1011) but not on the m-plane surfaces. The hillocks could be eliminated for the semipolar planes (not for the m-plane) by increasing the reactor pressure and lowering the growth temperature. Hillock free separate confinement laser structures emitting at 405 nm feature a very homgeneous luminescence in micro-PL and show amplified spontaneous emission under high power stripe excitation. Furthermore the In incorporation was found to be highest in QWs on (1011).