Effectiveness of TiN porous templates on the reduction of threading dislocations in GaN overgrowth by organometallic vapor-phase epitaxy

Abstract

We report on the reduction of threading dislocations in GaN overlayers grown by organometallic vapor phase epitaxy on micro-porous TiN networks. These networks were obtained by in situ annealing of thin Ti layers deposited in a metalization chamber, on the ͑0001͒ face of GaN templates. Observations by transmission electron microscopy indicate dislocation reduction by factors of up to 10 in GaN layers grown on TiN networks compared with the control GaN. X-ray diffraction shows that GaN grown on the TiN network has a smaller ͑102͒ plane peak width ͑4.6 arcmin͒ than the control GaN ͑7.8 arcmin͒. In low temperature photoluminescence spectra, a narrow excitonic full-width-at-half-maximum of 2.4 meV was obtained, as compared to 3.0 meV for the control GaN, confirming the improved crystalline quality of the overgrown GaN layers.

Crystal growth and characterization of AlGaN/GaN heterostructures prepared on vicinal-cut sapphire (0001) substrates

“…In other words, narrower (0 0 2) and (1 0 2) XRD peaks were achieved for the AlGaN/GaN epitaxial layers grown on 11-tilt sapphire substrate (i.e., sample A). It was known that the symmetrical XRD FWHM was most sensitive to the screw and/or mixed dislocations, while the asymmetrical XRD FWHM was related to the other dislocation such as edge dislocation [15,16]. Therefore, a narrower peak width of symmetrical and asymmetrical HRXRD rocking curves suggests that the crystalline quality of AlGaN/GaN films grown on vicinal-cut sapphire substrate is better than that of the same epi-structure grown on c-axis-oriented sapphire substrate.…”

Reducing dislocations of thick AlGaN epilayer by combining low-temperature AlN nucleation layer on c-plane sapphire substrates

“…The intensity of AlGaN (0 0 2) for sample B is much stronger than that of sample A. Previously, it has been demonstrated that the X-ray rocking curve for the symmetric (0 0 2)-reflecting plane is related to screw and mixed dislocations, whereas the X-ray rocking curve for the asymmetric (1 0 2)-reflecting plane is directly influenced by all threading dislocations, including edge dislocations [12][13][14]. We believe that the improved crystal quality is related to the alleviation of lattice mismatch between AlGaN and the underneath sapphire substrate.…”

Investigation on HT-AlN Nucleation Layers and AlGaN Epifilms Inserting LT-AlN Nucleation Layer on C-Plane Sapphire Substrate

“…As we know, the strain along the growth direction is found to be tensile as elasticity theory predicts in the case of biaxial stress [15][16][17][18]. By comparison to the number of V-shaped pits, more tensile strain can be relieved in the condition of more V-shaped pits on the surface of Sample B.…”