We have studied optical properties of GaN grown on sapphire by metalorganic chemical vapor deposition in the near band-edge energy range by cathodoluminescence. A large shift of the band-edge luminescence to lower energies is induced by increasing the beam energy. The free exciton position shifts about 20 meV when the beam energy is increased from 5 keV to 25 keV at room-temperature. The effect is explained by internal absorption caused by an exponential absorption tail at the band-edge. An Urbach parameter of about 30 to 40 meV for the exponential band-tail in our samples is estimated by comparing experimental with simulated spectra.
CITATION STYLE
Knobloch, K., Perlin, P., Krueger, J., Weber, E. R., & Kisielowski, C. (1998). Effect of internal absorption on cathodoluminescence from GaN. MRS Internet Journal of Nitride Semiconductor Research, 3. https://doi.org/10.1557/S1092578300000764
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