Mapping the composition-dependence of the energy bandgap of GaAsNBi alloys

Abstract

We have examined the alloy composition dependence of the energy bandgap and electronic states in GaAsNBi alloys. Using direct measurements of N and Bi mole fractions, via ion beam analysis, in conjunction with direct measurements of the out-of-plane misfit via x-ray rocking curves, we determine the “magic ratio” for lattice-matching of GaAsNBi alloys with GaAs substrates. In addition, using a combination of photoreflectance and photoluminescence spectroscopy, we map the composition- and misfit-dependence of the energy bandgaps, along with revealing the energetic position of Bi-related states at approximately 0.18 eV above the valence band maximum.

Raman scattering study on dilute nitride-bismide GaNAsBi alloys: behavior of photo-excited LO phonon-plasmon coupled mode

“…Consequently, the quaternary GaNAsBi alloy on GaAs can cover a wide spectral range of the nearinfrared with flexible control of the band offsets. 1,[4][5][6] In addition, this alloy can be lattice-matched to GaAs by controlling the composition of N and Bi. 1,6) Based on these advantages, optoelectronic devices, such as light-emitting diodes 7) and solar cells, 8) have been prototyped.…”

Temperature-dependent study of GaAs1−x−y N x Bi y alloys for band-gap engineering: photoreflectance and k · p modeling

“…It has been found that the molar ratio of nitrogen to bismuth for GaAsNBi matching to GaAs should be equal to 0.59, 21) although a recent paper suggests a revised value of 0.61. 22) The temperature dependence of the band-gap energy of semiconductors represents a basic material-specific property which is of substantial practical and also theoretical interest. It is well known that the band-gap of semiconductors decreases monotonically with increasing temperature due to dilation of the lattice constant and the temperature-dependent electron-phonon interaction.…”

“…Figure 1 shows the calculated band structure close to the Γ point of GaAs and a GaAs 0.926 N 0.018 Bi 0.056 alloy to illustrate the Bi-and N-induced band-gap reduction based on the previous report. 22) The calculation was carried out under the assumption that the valence band edge moves according to the valence band anticrossing (VBAC) model and the conduction band minimum shifts according to the CBAC model. 5,14) Figure 1 also depicts the localized Bi 6p-like states at 0.4 eV below the GaAs VBM (valence band maximum), spin-orbit split energy for the bismuth = -E 1.9 eV Bi SO below VBM of GaAs, and the resonant energy of nitrogen level E N = ∼1.65 eV above the top of the GaAs VBM.…”

“…Our previous work on GaAs 1−x−y N x Bi y alloys has shown a PR resonance separation on heavy-hole transition and light-hole transition at the Γ point of the Brillouin zone. 22) However, in these investigations, the valence band splitting is neglected for all samples since the two resonances are not well resolved because of worse spectral resolution in this set of samples and also due to probing place on a sample, where inhomogeneity was possibly much greater causing large broadening and weak intensity of the light-hole related transition. For most samples the resonance amplitude becomes the highest for intermediate temperatures which may indicate the carrier localization at low temperatures.…”

“…31) It can be a confirmation of the thesis of localized states proposed in our previous work. 22) Figures 3(a) and 3(b) show the temperature dependence of the band-gap extracted from the fitting procedure for all samples. It is clearly visible that the temperature-induced narrowing of the band-gap in GaAs 1−x−y N x Bi y alloys is significant in the range 20-300 K (∼82-95 meV) for the sample set with "constant" N and various Bi content [3(a)], and ∼66-99 meV for samples with "constant" Bi and various N content [3(b)].…”