AVS 51st International Symposium
    Semiconductors Wednesday Sessions
       Session SC-WeA

Invited Paper SC-WeA1
Growth and Properties of Dilute Nitride Semiconductors with a Bismuth Surfactant

Wednesday, November 17, 2004, 2:00 pm, Room 304C

Session: Narrow Gap Semiconductors
Presenter: T. Tiedje, University of British Columbia, Canada
Authors: T. Tiedje, University of British Columbia, Canada
D,A, Beaton, University of British Columbia, Canada
S. Tixier, University of British Columbia, Canada
M.B. Whitwick, University of British Columbia, Canada
E.C. Young, University of British Columbia, Canada
N.R. Zangenberg, University of British Columbia, Canada
S. Francoeur, National Renewable Energy Laboratory
Correspondent: Click to Email
The dilute nitride semiconductor In@suby@Ga@sub1-y@As@sub1-x@N@subx@ is a promising new III-V alloy for solar cells and lasers in which low concentrations of N cause an anomalous reduction in the bandgap. N alloying degrades the electronic properties, possibly through formation of localized N cluster states. We show that the electronic properties of GaAs@sub1-x@N@subx@ can be improved with the use of a Bi surfactant during plasma assisted MBE growth. The effect of modifying the active nitrogen species (ratio of atoms to excited state molecules) in plasma-assisted MBE growth has also been explored. The Bi surfactant reduces the surface roughness by a factor of ten and produces step flow growth at temperatures as low as 460°C. The surfactant also improves the room temperature photoluminescence (PL) efficiency in as-grown and annealed samples, and reduces the density of shallow gap states, as determined from the shape of the PL spectra. The N incorporation increases with the Bi coverage by up to 50% when the surface is saturated with Bi. In-situ mass spectroscopy experiments show that NAs (but not NBi) is present in the gas phase, during growth and that the partial pressure of NAs increases slightly with Bi flux, suggesting that the Bi surface layer enhances the reaction of active nitrogen with GaAs. The Bi covers the surface but does not incorporate (<2x10@super17@ cm@super-3@) under normal growth conditions, in which there is an As overpressure and the substrate temperature is @>@450°C. If the As:Ga flux ratio is reduced to approximately 1:1, Bi will incorporate at low substrate temperatures (380°C). The dilute Bi alloys show room temperature photoluminescence @footnote1@ and similar to the dilute nitrides the bandgap has an anomalously large concentration dependence. @FootnoteText@ @footnote1@S. Tixier et al, Appl. Phys. Lett. 82, 2245 (2003).