Filters

2020 - 20222

More filters

2021 - 20222
Reset filters

Settings

End date: 2024 × Start date: 2020 × DDC: 530 × Publisher: New York, NY : American Inst. of Physics × Subject: III-V semiconductors ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    High-temperature annealing of AlN films grown on 4H-SiC
    (New York, NY : American Inst. of Physics, 2020) Brunner, F.; Cancellara, L.; Hagedorn, S.; Albrecht, M.; Weyers, M.
    The effect of high-temperature annealing (HTA) at 1700 °C on AlN films grown on 4H-SiC substrates by metalorganic vapor phase epitaxy has been studied. It is shown that the structural quality of the AlN layers improves significantly after HTA similar to what has been demonstrated for AlN grown on sapphire. Dislocation densities reduce by one order of magnitude resulting in 8 × 108 cm-2 for a-type and 1 × 108 cm-2 for c-type dislocations. The high-temperature treatment removes pits from the surface by dissolving nanotubes and dislocations in the material. XRD measurements prove that the residual strain in AlN/4H-SiC is further relaxed after annealing. AlN films grown at higher temperature resulting in a lower as-grown defect density show only a marginal reduction in dislocation density after annealing. Secondary ion mass spectrometry investigation of impurity concentrations reveals an increase of Si after HTA probably due to in-diffusion from the SiC substrate. However, C concentration reduces considerably with HTA that points to an efficient carbon removal process (i.e., CO formation). © 2020 Author(s).
  • Thumbnail Image
    Item
    Long-term stability of GaAs/AlAs terahertz quantum-cascade lasers
    (New York, NY : American Inst. of Physics, 2022) Schrottke, L.; Lü, X.; Biermann, K.; Gellie, P.; Grahn, H.T.
    We have investigated high-performance GaAs/AlAs terahertz (THz) quantum-cascade lasers (QCLs) with respect to the long-term stability of their operating parameters. The output power of lasers that contain an additional, thick AlAs refractive-index contrast layer underneath the cascade structure decreases after three months by about 35%. The deterioration of these lasers is attributed to the oxidation processes in this contrast layer starting from the facets. However, GaAs/AlAs THz QCLs with an Al0.9Ga0.1As refractive-index contrast layer exhibit long-term stability of the operating parameters over many years even when they are exposed to atmospheric conditions. Therefore, these lasers are promising high-power radiation sources in the terahertz spectral region for commercial applications.