Spectroscopic transmission ellipsometry studies of intersub-band transitions in n-GaAs/Al0.3Ga0.7As quantum wells

Transmission ellipsometry at the Brewster angle of incidence is shown to combine the high sensitivity of ellipsometric parameters to spectral changes in the dielectric response with the possibility of efficiently p polarization sensitive transitions in a high index sample. The ellipsometrically measured polarization ratio is related to the transfer matrix elements, the GaAs/AlAs multilayer stack being treated as a uniaxial layer, composed of isotropic barriers and anisotropic well layers, grown on top of an isotropic substrate. The inversion problems is solved to determine the extraordinary dielectric response. The above has been applied to the case of intersub-band transitions between the first quantized and second upper-lying conduction band states in a 60-period n-GaAs(88 A)/Al0. 3Ga0.7As(130 A) quantum well detector-like stack, grown on a semi-insulating GaAs substrate. The dielectric response of the quantum well region to p-polarizec incident radiation has been extracted from the experimental data.