Abstract
M.O.V.P.E. grown GaAlAs/GaAs heterojunctions have been examined by modulation spectroscopy (electro reflectance - E R) in the E0, E0 + Ɗ0 region of both materials and compared with spectroscopic ellipsometry (S.E.) analysis in the 1.6 - 5.4 eV region. The electro-reflectance structures of thin layer (below 100 Å) of GaAlAs and GaAs are well resolved, even at room temperature. The "normal" (thin GaAlAs layer on top of GaAs substrate) and "inverted" (thin GaAs layer on top of GaAlAs thick film) heterostructures are analyzed using both techniques. Informations about composition, interface region and layer quality are obtained. The respective advantages and limitations of the two techniques are discussed.