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HL: Fachverband Halbleiterphysik
HL 47: GaN: preparation and characterization I
HL 47.2: Talk
Thursday, February 28, 2008, 14:15–14:30, EW 202
Defect structure in m-plane GaN grown on LiAlO2 using metalorganic and hydride vapour phase epitaxy — •Tim Wernicke1, Anna Mogliatenko3, Carsten Netzel1, Eberhard Richter1, Arne Knauer1, Frank Brunner1, Markus Weyers1, Wolfgang Neumann3, and Michael Kneissl1,2 — 1FBH Berlin, Germany — 2Institute of Solid State Physics, TU Berlin, Germany — 3AG Kristallographie, Institut für Physik, HU Berlin, Germany
The FWHM of symmetric (1010) XRD rocking curves of m-plane GaN grown on LiAlO2 is anisotropic. By investigating the microstructure with transmission electron microscopy (TEM) we identifid basal plane stacking faults (BSF) and stacking mismatch boundaries (SMB) in the GaN layers. BSFs are aligned in-plane along the a-direction and therefore cause an anisotropic broadening of the FWHM(1010) with incidence along [0001]. SMBs have no preferential direction and hence result in an isotropic broadening of the FWHM(1010). We observed that this anisotropy can be reduced by lowering the MOVPE growth temperature. We propose that the lowering of the growth temperature leads to a reduction of BSFs which is accompanied by an increase in SMBs. The MOVPE grown layers were used as templates for the growth of 200 µ m thick m-plane GaN layers by HVPE. During HVPE growth the LiAlO2 substrate thermally decomposed and peeled off after cool-down. On the surface a network of cracks not being aligned to crystallographic directions was found. The layers were not transparent probably due to metallic Ga inclusions and exhibited an asymmetric bow according to the lattice anisotropy of the (100) LiAlO2 surface.