@article {12196, title = {Pressure Controlled GaN MBE Growth Using a Hollow Anode Nitrogen Ion Source}, journal = {Materials Research Society Proceedings}, volume = {449}, year = {1997}, note = {

1996 MRS Fall Meeting

}, abstract = {

GaN films were grown on sapphire substrates at temperatures below 1000 K utilizing a Hollow Anode nitrogen ion source. A Ga flux limited growth rate of ~0.5 μm/h is demonstrated. Active utilization of strain and the assistance of a nitrogen partial pressure during buffer layer growth are found to be crucial issues that can improve the film quality. The best films exhibit a full width at half maximum of the x-ray rocking curves of 80 arcsec and 1.85 meV for the excitonic photoluminescence measured at 4 K. A Volmer-Weber three dimensional growth mode and the spontaneous formation of cubic GaN inclusions in the hexagonal matrix are observed in the investigated growth temperature range. It is argued that this growth mode contributes to a limitation of the carrier mobility in these films that did not exceed 120 cm2/Vs through a minimum canier concentration of ~1015 cm-3 was achieved.

}, doi = {10.1557/PROC-449-221}, author = {Michael S.H. Leung and Ralf Klockenbrink and Christian F. Kisielowski and Hiroaki Fujii and Joachim Kr{\"u}ger and Sudhir G. Subramanya and Andr{\'e} Anders and Zuzanna Liliental-Weber and Michael D. Rubin and Eicke R. Weber}, editor = {Joachim Kr{\"u}ger} } @article {1849, title = {Strain Related Phenomena in GaN Thin Films}, journal = {Physical Review B}, volume = {54}, number = {24}, year = {1996}, month = {12/1996}, pages = {17745-17753}, chapter = {17745}, abstract = {

Photoluminescence (PL), Raman spectroscopy, and x-ray diffraction are employed to demonstrate the co-existence of a biaxial and a hydrostatic strain that can be present in GaN thin films. The biaxial strain originates from growth on lattice-mismatched substrates and from post-growth cooling. An additional hydrostatic strain is shown to be introduced by the presence of point defects. A consistent description of the experimental results is derived within the limits of the linear and isotropic elastic theory using a Poisson ratio nu =0.23+/-0.06 and a bulk modulus B=200+/-20 GPa. These isotropic elastic constants help to judge the validity of published anisotropic elastic constants that vary greatly. Calibration constants for strain-induced shifts of the near-band-edge PL lines with respect to the E2 Raman mode are given for strain-free, biaxially strained, and hydrostatically contracted or expanded thin films. They allow us to extract differences between hydrostatic and biaxial stress components if present. In particular, we determine that a biaxial stress of one GPa would shift the near-band-edge PL lines by 27+/-2 meV and the E2 Raman mode by 4.2+/-0.3 cm-1 by use of the listed isotropic elastic constants. It is expected from the analyses that stoichiometric variations in the GaN thin films together with the design of specific buffer layers can be utilized to strain engineer the material to an extent that greatly exceeds the possibilities known from other semiconductor systems because of the largely different covalent radii of the Ga and the N atom.

}, doi = {10.1103/PhysRevB.54.17745}, author = {Christian F. Kisielowski and Joachim Kr{\"u}ger and Sergei Ruvimov and Tadeusz Suski and Joel W. Ager III and Erin C. Jones and Zuzanna Liliental-Weber and Michael D. Rubin and Eicke R. Weber and Michael D. Bremser and Robert F. Davis}, editor = {Joachim Kr{\"u}ger} } @conference {11890, title = {Fundamental Materials-Issues Involved in the Growth of GaN by Molecular Beam Epitaxy}, year = {1994}, abstract = {

Gallium nitride is one of the most promising materials for ultraviolet and blue light-emitting diodes and lasers. Both Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) have recently made strong progress in fabricating high-quality epitaxial GaN thin films. In this paper, we review materials-related issues involved in MBE growth. We show that a strong understanding of the unique meta-stable growth process allows us to correctly predict the optimum conditions for epitaxial GaN growth. The resulting structural, electronic and optical properties of the GaN films are described in detail.

}, author = {Nathan Newman and T.C. Fu and Z. Liu and Zuzanna Liliental-Weber and Michael D. Rubin and James S. Chan and Erin C. Jones and Jennifer T. Ross and Ian M. Tidswell and Kin Man Yu and Nathan W. Cheung and Eicke R. Weber} }