Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 52: Nonpolar and Semipolar Nitrides
HL 52.2: Talk
Wednesday, March 16, 2011, 12:00–12:15, POT 51
Single phase semipolar (1122) GaN on (1010) sapphire — •S. Ploch1, J. B. Park2, J. Stellmach1, T. Schwaner1, M. Frentrup1, T. Wernicke1, T. Niermann2, M. Pristovsek1, M. Lehmann2, and M. Kneissl1 — 1Institute of Solid States Physics, — 2Institute of Optics and Atomic Physics, TU Berlin, Hardenbergstr. 36, 10623 Berlin
InGaN quantum well based light emitters grown on (0001) GaN suffer from poor quantum efficiencies with increasing indium mole fraction due to strong polarization fields along the polar crystal orientation. This effect can be greatly reduced by growing on semi- and non-polar GaN orientations. Semipolar (1122) GaN layers were deposited by metalorganic vapour phase epitaxy on (1010) sapphire. After sapphire substrate nitridation at 1000∘C, a GaN nucleation layer was deposited at high temperature, followed by the deposition of 1.5 nm thick GaN buffer layers. The samples show predominantly (1122) orientation with a small fraction of (1013) oriented domains. With increasing nitridation layer thickness the (1013) phase is suppressed leading to a very smooth surface morphology (rms roughness < 4nm). PL measurements show dominant basel plane stacking fault (BSF) I1 luminescence without any other defects. Transmission electron microscopy measurements reveal a high BSF density. The FWHM of the X-ray diffraction rocking curve measurements of the (1122) reflection decreases to 1193 arcsec and 739 arcsec along [1100] and [1123] respectively with increasing nucleation temperature. Using high temperature nucleation smooth and homogeneous (1122) phase GaN layers have been obtained.