Optical interference effect of a thick absorbing LT-GaAs layer on a Bragg reflector
Near-infrared reflectance spectra of 5 μm thick low-temperature (LT) GaAs films on GaAs/AlAs Bragg reflectors (BRs) have been studied by model calculations as a function of the linear absorption coefficient of the films αf. With increasing αf, the reflectance of the stop band decrease monotonously. In contrast, the interference modulation due to the LT-GaAs layer on the BR inside of the stop band increases with increasingαf until 1×103 cm−1 and decreases for larger αf. This unusual behavior of the Fabry–Perot features in the stop band is explained by the attenuation of the light in the film as well as by the interference in the case of destructive superposition between the partial waves, which are strongly reflected at the film/BR interface, and those partial waves, which are much more weakly reflected at the air/film interface.
Source: Materials Science in Semiconductor Processing