Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 33: GaN: Preparation and characterization
HL 33.2: Vortrag
Mittwoch, 29. März 2006, 14:45–15:00, BEY 154
Critical points of the band structure of AlN/GaN superlattices investigated by spectroscopic ellipsometry and modulation spectroscopy — •C. Buchheim1, R. Goldhahn1, A. T. Winzer1, C. Cobet2, M. Rakel2, N. Esser2, U. Rossow3, D. Fuhrmann3, and A. Hangleiter3 — 1Institute of Physics, Technical University Ilmenau, PF 100565, 98684 Ilmenau, Germany — 2Institute of Analytical Sciences, Department Berlin-Adlershof, Albert-Einstein-Str. 9, 12489 Berlin, Germany — 3Institute of Applied Physics, Technical University Braunschweig, Mendelssohnstr. 2, 38106 Braunschweig, Germany
AlN/GaN superlattices (SL) are suitable for the design of distributed Bragg reflectors and optical devices based on intersubband transitions. Applications are light emitters in the near to mid infrared region, quantum well infrared photodetectors and quantum cascade laser structures. For the design of such heterostructures and their evaluation the detailed knowledge of their optical properties over an extended energy range is essential. Three AlN/GaN SLs with different barrier and well thicknesses were investigated by modulation spectroscopy and photoluminescence to determine their ground state transition. A shift of the transition energies in dependence of the barrier and well width is found. The results are compared to quantum mechanical calculations at the Brillouin zone centre. In addition the dielectric function is determined by spectroscopic ellipsometry from the infrared to the vacuum ultraviolet spectral range (0.75 - 9.8 eV). Quantum confinement effects are observed not only for the band gap, but also for the higher energetic critical points of the band structure as can be seen from the comparison to AlGaN alloys.