Premium
Surface morphology of homoepitaxial GaN grown on non‐ and semipolar GaN substrates
Author(s) -
Wernicke Tim,
Ploch Simon,
Hoffmann Veit,
Knauer Arne,
Weyers Markus,
Kneissl Michael
Publication year - 2011
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201046346
Subject(s) - hillock , materials science , bar (unit) , morphology (biology) , epitaxy , surface diffusion , optoelectronics , crystallography , nanotechnology , composite material , chemistry , layer (electronics) , meteorology , physics , organic chemistry , adsorption , biology , genetics
GaN layers on bulk m ‐plane, $(11{\bar {2}}2)$ , $(10{\bar {1}}2)$ and $(10{\bar {1}}1)$ GaN substrates were grown by metal organic vapor phase epitaxy. XRD rocking curves have a FWHM of less than 150″, indicating excellent crystalline quality. However in many cases surface morphology exhibits hillocks with a height of 1–2 µm and a lateral extension of 50–200 µm whereas a smooth surface would be desirable for optoelectronic devices. The influence of growth parameters on the surface morphology was studied. The goal was, to constrain the material redistribution, that is necessary to form large hillocks. This was achieved by lowering the adatom diffusion length by a reduction of temperature and an increased reactor pressure. In the case of the $(10{\bar {1}}1)$ and $(10{\bar {1}}2)$ semipolar planes a reduction of the adatom diffusion length leads to a reduction of hillock density, hillock size and a smoother surface between hillocks. However, the m ‐plane surface does not react to a reduction of adatom mobility. Even at 890°C and 400 mbar rectangular pyramids cover the surface. In contrast to the other planes, the $(11{\bar {2}}2)$ becomes instable, when the adatom diffusion length is reduced.