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HL: Fachverband Halbleiterphysik

HL 47: GaN: preparation and characterization I

HL 47.2: Vortrag

Donnerstag, 28. Februar 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 Kneissl^1,2 — 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.