The influence of buffer layer coalescence on stress evolution in GaN grown on ion implanted AlN/Si(111) substrates

• Published in: Journal of crystal growth 2014-05, Vol.393, p.98-102
• Main Authors: Gagnon, Jarod C., Leathersich, Jeffrey M., Shahedipour-Sandvik, Fatemeh (Shadi), Redwing, Joan M.
• Format: Article
• Language: English
• Subjects: A1. Organometallic vapor phase epitaxy; A1. Stresses; A1. Substrates; Aluminum nitride; B1. Gallium compounds; B1. Nitrides; B2. Semiconducting III–V materials; Buffer layers; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Coalescence; Compressive properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Defects and impurities in crystals; microstructure; Exact sciences and technology; Gallium nitrides; Instruments for strain, force and torque; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Linear defects: dislocations, disclinations; Materials science; Mechanical instruments, equipment and techniques; Methods of crystal growth; physics of crystal growth; Methods of deposition of films and coatings; film growth and epitaxy; Morphology; Physics; Silicon substrates; Stresses; Structure of solids and liquids; crystallography; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2013.08.031

The effect of AlN buffer layer morphology on the evolution of growth stress in GaN epilayers deposited by metalorganic chemical vapor deposition on N+ ion-implanted AlN/Si(111) substrates was investigated. AlN buffer layers were grown using either a continuous or pulsed source flow process which altered the grain size and extent of coalescence of the films. In situ stress measurements revealed that substrate implantation reduced the initial compressive stress in the GaN epilayers likely due to a decoupling of the AlN lattice from the underlying crystalline Si substrate. The buffer layer morphology was found to significantly alter the influence of ion-implantation on the film properties. GaN epilayers grown on ion-implanted AlN/Si(111) substrates prepared with the pulsed conditions exhibited a 63% decrease in threading dislocation (TD) density compared to unimplanted substrates. In addition, these films were observed to grow under a low overall stress compared to the other samples which exhibited a more typical compressive to tensile stress transition during growth. The low overall growth stress of the GaN grown on the implanted pulsed AlN/Si(111) was explained in terms of a reduced strain gradient from dislocation inclination.