| AVS 57th International Symposium & Exhibition | |
| Actinides and Rare Earths Topical Conference | Monday Sessions |
| Session AC+TF-MoA |
| Session: | Actinide and Rare Earths Thin Films |
| Presenter: | S.R. McHale, Air Force Institute of Technology |
| Authors: | S.R. McHale, Air Force Institute of Technology J.W. McClory, Air Force Institute of Technology J.C. Petrosky, Air Force Institute of Technology Y.B. Losovyj, Louisiana State University |
| Correspondent: | Click to Email |
Au-YbGaN Schottky barrier formation was observed using Au evaporation on multiple concentrations of YbxGa1-xN thin films deposited on (111) Si substrates. Low Energy Electron Diffraction was performed to verify the integrity of the Au deposition. Energy dependent, synchrotron generated photoemission spectroscopy ranging from 15 to 26 eV under UHV conditions clearly determined a valence band shift of up to 0.62 eV.
The experiments were conducted at the Louisiana State University (LSU) Center for Advanced Microstructures and Devices (CAMD), using synchrotron radiation dispersed by the 3m toroidal grating monochromator (TGM) beamline, where resolution of the experimental apparatus is approximately 70 meV. Thin films were fabricated using RF plasma-assisted molecular beam expitaxy (PAMBE) at the University of Nebraska (Lincoln) Center for Materials and Nanoscience (NCMN). Yb temperatures during deposition were 500 ∘C, 700 ∘C, and 860 ∘C, resulting in slightly coarse, uniform, and very coarse grained films, respectively. The XRD patterns show a high degree of order in the films.
A least squares fit was used to calculate the valence band maximum (VBM) for each spectrum. Comparing the calculated VBM values for the bare YbGaN sample spectra with those following Au deposition shows that Au clearly affects the YbGaN electronic structure by shifting the valence band toward the Fermi energy by a maximum value of 0.62 eV at a monolayer of Au coverage. This valence band shift yields a calculated Schottky Barrier, qφB, of 0.83 eV, determined by the relationship Eg - (EF - EVBM), where the energy gap, Eg, was approximated at 3.5 eV.
SB calculation via direct spectroscopic data will be supplemented by SB calculation via I-V measurements of the sample surface, using a Keithley 4200 Semiconductor Characterization System and a Signatone Probe Station.
Our research efforts are motivated by radiation detection materials and devices. Radiation detector diodes typically operate in the reverse bias mode, where Schottky contacts are desirable to optimize the signal-to-noise ratio. Therefore, we intend to extend these results to facilitate additional measurements using other Lanthanide-doped III-nitride compounds in a future research endeavor involving potential radiation detection materials. We anticipate that this effort will improve researchers' determination of suitable combinations of materials, and will produce novel, efficient, and more accurate neutron detection devices than currently available.