Accession Number : ADA549030


Title :   The Effects of Rare Earth Doping on Gallium Nitride Thin Films


Descriptive Note : Doctoral thesis


Corporate Author : AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT


Personal Author(s) : McHale, Stephen R


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a549030.pdf


Report Date : Sep 2011


Pagination or Media Count : 182


Abstract : The thermal neutron capture cross section of the rare earth (RE) metal isotope Gd-157 is the largest of all known natural elements, which distinguishes the material as a logical candidate for neutron detection. To address an incomplete understanding of rare earth doped Gallium Nitride (GaN) materials, investigations of the surface electronic structure and interface properties of GaN thin films doped with rare earths (Yb, Er, Gd) were undertaken. Lattice ion occupation, bonding, rare earth 4f occupation, and gold Schottky barrier formation were examined using synchrotron photoemission spectroscopy. Measured Debye temperatures indicate substitutional occupation of Ga sites by RE ions. The occupied RE 4f levels, deep within the valence band, suggest that intra-atomic f-f transitions may be more 'blue' than predicted by theoretical models. Thin layers of gold did not wet and uniformly cover the GaN surface, even with rare earth doping of the GaN. The resultant Schottky barrier heights for GaN:Yb, GaN:Er, and GaN:Gd, are 25-55% larger than those reported at the gold to undoped GaN interface. The utility of gadolinium as a neutron detection material was examined via fundamental nuclear and semiconductor physics. Low charge production and the large range of internal conversion electrons limits charge collection efficiency.


Descriptors :   *DOPING , *GALLIUM NITRIDES , *RARE EARTH ELEMENTS , DETECTION , GOLD , NEUTRON DETECTORS , THESES , THIN FILMS


Subject Categories : Solid State Physics


Distribution Statement : APPROVED FOR PUBLIC RELEASE