J. Sik et al., Near-band-gap optical functions spectra and band-gap energies of GaNAs/GaAs superlattice heterostructures measured by spectroscopic ellipsometry, APPL PHYS L, 76(20), 2000, pp. 2859-2861
The optical properties of GaAs/GaNxAs1-x superlattice structures grown by m
etal-organic vapor-phase epitaxy are studied by variable angle-of-incidence
spectroscopic ellipsometry for photon energies from 0.75 to 1.55 eV. We em
ploy Adachi's critical-point composite model, and we report the direct-band
-gap energy E-0 and the complex index of refraction of the GaNxAs1-x sublay
ers for x less than or equal to 3.3% from analysis of the ellipsometry data
. We observe a strong redshift of E-0 with increase in x, and a strong decr
ease of the E-0 transition amplitude. The E-0 values obtained for the super
lattice structures are in good agreement with photoluminescence results, an
d also with previous reports from single epilayers. Structure, composition,
layer thickness, and parallel and perpendicular lattice mismatch of the sa
mples are studied by transmission electron microscopy and high-resolution x
-ray diffraction investigations. (C) 2000 American Institute of Physics. [S
0003-6951(00)02420-7].