Abstract
We present results of electronic structure calculations on the N-related localized vibrational modes in the dilute nitride alloy GaSb1−xNx. By calculating the formation energies of various possible N incorporation modes in the alloy, we determine the most favorable N configurations, and we calculate their vibrational mode frequencies using density functional theory under the generalized gradient approximation to electron exchange and correlation, including the effects of the relativistic spin-orbit interactions. For a single N impurity, we find substitution on an Sb site, NSb, to be most favorable, and for a two-N-atom complex, we find the N-N split interstitial on an Sb site to be most favorable. For these defects, as well as, for comparison, defects comprising two N atoms on neighboring Sb sites and a N-Sb split interstitial on an Sb site, we find well-localized vibration modes (LVMs), which should be experimentally observable. The frequency of the triply degenerate LVM associated with NSb is determined to be 427.6 cm−1. Our results serve as a guide to future experimental studies to elucidate the incorporation of small concentrations of N in GaSb, which is known to lead to a reduction of the band gap and opens the possibility of using the material for long-wavelength applications.
Highlights
Dilute nitride alloys have been the focus of much experimental and theoretical study over the past two decades, both for their potential device applications and their unusual physical properties
When a small fraction of the As ions in GaAs or GaInAs are replaced with nitrogen, there is a considerable redshift in the band gap, with a 1% concentration of N leading to a band-gap reduction of approximately 150 meV [1,2], which opens up the possibility of long-wavelength telecommunications based on GaAs substrates [3,4], and of pushing the wavelength range of GaAs-based solar cells further into the infrared (IR) [5]
Our calculated bulk modulus B and elastic constants C11, C12, and C44 are lower than experiment, by ∼9% for B when compared with the room-temperature measurement of McSkimin et al [89], and by ∼6% for the elastic constants in comparison with the low-temperature measurements of Boyle and Sladek [90], but they are within the same level of accuracy as previous calculations at a similar level of theory [91,92,93,94,95]
Summary
Dilute nitride alloys have been the focus of much experimental and theoretical study over the past two decades, both for their potential device applications and their unusual physical properties. When a small fraction of the As ions in GaAs or GaInAs are replaced with nitrogen, there is a considerable redshift in the band gap, with a 1% concentration of N leading to a band-gap reduction of approximately 150 meV [1,2], which opens up the possibility of long-wavelength telecommunications based on GaAs substrates [3,4], and of pushing the wavelength range of GaAs-based solar cells further into the infrared (IR) [5] Associated with this decrease in band gap, is a substantial decrease in n-type carrier mobility, with mobilities of ∼200 cm (V s)−1, that are too low for many device applications at present, being typically found in samples [6,7,8,9].
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