Modeling and extraction of optical characteristics of InAs/GaSb strained layer superlattice

With the increasing use of resonant structures in optical devices, broadband optical characterization of the refractive index and extinction coefficient is necessary for accurate simulation and device design. For resonance-enhanced photodetectors, the complex refractive index is necessary to impedance match not only the resonator to air, minimizing the reflection, but also the resonator to the detector element, ensuring absorption occurs in the photodiode. To work towards better resonator-detector coupling, we present the complex refractive index for GaSb and an InAs/GaSb strained layer superlattice designed to be the absorber layer for a long-wave infrared photodetector. The optical properties were extracted using spectroscopic ellipsometry. Several modeling methods will be discussed for both the superlattice and the single-side polished bulk GaSb. Comparison to transmission and reflection values as well as absorption coefficients from literature provide additional confidence in the extraction process. Future work will incorporate these values into a resonance-enhanced photodetector.