Optical anisotropy of (11N) GaAs/GaAlAs superlattices

The in-plane anisotropy of a series of (113), (115), (001) vicinal, and singular (001) oriented GaAs/Ga0.7Al0.3As superlattices (SLʹs) has been studied by reflectance difference spectroscopy (RDS) in the photon energy range covering both the E0 and the E1 energies of GaAs, and from 80 to 300 K. The polarity and the energy position of the observed RDS resonances near the E0 energy confirm that these resonances are indeed originated from the heavy hole (HH), the light hole (LH), and the Γ7 LH subbands in the GaAs wells. The transition strength anisotropy is in agreement with the multiband k * p model calculations. Sizable RD resonances have been observed in the (100) singular SLʹs at low temperatures, which are believed to be due to the HH and the LH exciton bound to anisotropic interface structural defects. The optical anisotropy of the SLʹs near the E1 critical energy of GaAs shows complicated resonance patterns. Some of the resonances occur below the E1 energy, which the simple effective-mass theory for the L-point states cannot explain.