Anti-reflection coatings for photodetectors to reduce the reflectance in the SWIR range

The anti-reflection coating or coatings plays an important role in the performance of optoelectronic devices. With the help of a database of the material’s optical parameters and simulation software, an anti-reflection coating was developed to optimize the absorption of incident photons on InP-based devices. The anti-reflection coating consists of 4 alternating layers of SiO
2
and TiO
2
, deposited by sputtering. Characterization techniques were used to calibrate the depositions and investigate the optical properties of these layers. The two techniques used were ellipsometry (measurements of thickness and refractive index) and spectrophotometry (thickness and reflectance). The reflectance results show a reduction in reflectance of approximately 90% compared to bare InP, for wavelengths longer than 1300 nm.