@article {11964, title = {The Influence of Nitrogen Ion Energy on the Quality of GaN Films Grown with Molecular Beam Epitaxy}, journal = {Journal of Electronic Materials}, volume = {24}, number = {4}, year = {1995}, month = {04/1995}, pages = {249-255}, chapter = {249}, abstract = {

Since the growth of GaN using molecular beam epitaxy (MBE) occurs under metastable growth conditions, activated nitrogen is required to drive the forward synthesis reaction. In the process of exciting the nitrogen using a plasma or ion-beam source, species with large kinetic energies are generated. Impingement on the growth surface by these species can result in subsurface damage to the growing film, as well as an enhancement of the reverse decomposition reaction rate. In this study, we investigate the effect of the kinetic energy of the impinging nitrogen ions during growth on the resulting optical and structural properties of GaN films. Strong band-edge photoluminescence and cathodoluminescence are found when a kinetic energy of ~10 eV are used, while luminescence is not detectable when the kinetic energies exceeds 18 eV. Also, we find that the use of conductive SiC substrates results in more homogeneous luminescence than the use of insulating sapphire substrates. This is attributed to sample surface charging in the case of sapphire substrates and subsequent variation in the incident ion flux and kinetic energy across the growth surface.This study clearly shows that the quality of GaN films grown by MBE are presently limited by damage from the impingement of high energy species on the growth surface.

}, keywords = {Activated nitrogen, GaN, molecular beam epitaxy (MBE), nitrogen ion energy}, issn = {0361-5235}, doi = {10.1007/BF02659683}, author = {T.C. Fu and Nathan Newman and Erin C. Jones and James S. Chan and Xiaohong Liu and Michael D. Rubin and Nathan W. Cheung and Eicke R. Weber} } @article {1900, title = {Thermal Annealing Characteristics of Si and Mg-implanted GaN Thin Films}, journal = {Applied Physics Letters}, volume = {68}, number = {19}, year = {1995}, month = {03/1996}, pages = {2702-2704}, chapter = {2702}, abstract = {

In this letter, we report the results of ion implantation of GaN using 28Si and 23Mg species. Structural and electrical characterizations of the GaN thin films after thermal annealing show that native defects in the GaN films dominate over implant doping effects. The formation energies of the annealing induced defects are estimated to range from 1.4 to 3.6 eV. A 30 keV10^14 cm-2 Mg implant results in the decrease of the free-carrier concentration by three orders of magnitude compared to unimplanted GaN up to an annealing temperature of 690 {\textdegree}C. Furthermore, we have observed the correlation between these annealing-induced defects to both improved optical and electrical properties.

}, keywords = {annealing, crystal doping, defect states, electrical properties, gallium nitrides, ion implantation, magnesium additions, microstructure, silicon additions}, issn = {0003-6951}, doi = {10.1063/1.116314}, author = {James S. Chan and Nathan W. Cheung and Lawrence F. Schloss and Erin C. Jones and William S. Wong and Nathan Newman and Xiaohong Liu and Eicke R. Weber and A. Gassman and Michael D. Rubin} } @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} } @conference {11636, title = {Comparison of AIN Films Grown by RF at Magnetron Sputtering and Ion-Assisted Molecular Beam Epitaxy}, booktitle = {Materials Research Society}, volume = {300}, year = {1993}, month = {04/1993}, address = {San Francisco, CA}, abstract = {

Crystalline aluminum nitride (AlN) thin films were formed on various substrates by using RF magnetron sputtering of an A1 target in a nitrogen plasma and also by ion-assisted molecular beam epitaxy (IAMBE). Basal-oriented AlN/(111) Si showed a degradation of crystallinity with increased substrate temperature from 550 to 770 {\textdegree}C, while the crystallinity of AlN/(0001) Al2O3 samples improved from 700 to 850 {\textdegree}C. The optical absorption characteristics of the AlN/(0001) Al2O3 films as grown by both deposition methods revealed a decrease in sub-band gap absorption with increased substrate temperature.

}, author = {James S. Chan and T.C. Fu and Nathan W. Cheung and Jennifer T. Ross and Nathan Newman and Michael D. Rubin} }