Dislocation generation at the coalescence of aluminum nitride lateral epitaxy on shallow-grooved sapphire substrates

Abstract

The joining of defect-free AlN stripes is observed to trigger the generation of a large density of threading dislocations in the vicinity of the coalescence point. The AlN structure was grown by pulsed lateral epitaxy on shallow-grooved sapphire substrates. In the precoalescence stage, the dislocation density in the lateral epitaxial region (<108cm−2) is over two orders of magnitude less than in standard c-plane epitaxy. Basal-plane dislocations (b=a=13<112¯0>) are generated at the coalescence point as a result of relaxation of compressive stress that develops due to temperature gradients during growth. They bend toward the surface during the postcoalescence growth stage, leading to a high density of pure-edge threading dislocations in the lateral growth regions. Some threading dislocations form loops on prismatic planes in the crystal and the basal segments are observed to glide in the [0001] direction under the electron beam in the microscope.

Hot-Wall MOCVD for Highly Efficient and Uniform Growth of AlN

“…SiC and sapphire are the only widely available substrates for AlGaN epitaxy. To improve device performance, use of dislocation reduction techniques such as epitaxial lateral overgrowth (ELO) is demanding, especially elaborative maskless ELO techniques 3,4 to prevent interaction of Al with the SiO 2 or SiN X mask materials and enhance the lateral growth rate of AlGaN. 5 A major issue of the AlGaN technology is development of the vapor-phase growth process including both hydride vapor phase epitaxy, HVPE, for growth of thick layers and metal-organic vapor-phase epitaxy, MOVPE (or alternatively metal-organic chemical vapor deposition, MOCVD), for heterostructure device fabrication.…”

High-quality AlN epitaxy on nano-patterned sapphire substrates prepared by nano-imprint lithography

“…Besides, epitaxial lateral overgrowth (ELO) techniques on micro-stripe patterned sapphires or AlN/sapphire templates have also attracted much attention and significantly reduced the TDD56789. However, large spacing between micro-patterns usually requires a great coalescence thickness close to 10 μm, implying long growth time and high cost.…”

Morphological evolution during epitaxial lateral overgrowth of indium phosphide on silicon

“…Stacking faults also grow in size as the thickness of the layer increases, and when they intersect they may give rise to new threading dislocations, although the mask itself filters the threading dislocations from its underlying regions [19,20]. That the threading dislocations can also arise from the coalescence points has been revealed in AlN growth studies by Mei et al [21].…”