Micropyramidal Si Photonics–A Versatile Platform for Detector and Emitter Applications

Abstract Anisotropic wet etching of silicon (Si) has been known for decades, but the extraordinary capabilities of this technology to provide highly ordered microphotonic arrays have received limited attention in previous studies. It is shown that these capabilities include: i) a unique self‐terminating etching nature − crucial for achieving uniform arrays over centimeter‐scale wafers, ii) an extraordinary smoothness of the slow‐etching (111) planes, and iii) a precise geometry control including the extent micropyramids or micropyramidal voids are truncated. The combination of these properties transforms this technology into a versatile platform for novel detector and emitter applications in Si photonics. The optical properties of such arrays are studied by finite‐difference time‐domain modeling in two realms represented by different boundary conditions (BCs). Periodic BCs result in Talbot self‐images experimentally observed in this work. Perfectly matched layer BCs describe mesoscale interference effects resulting in the subwavelength focusing properties of micropyramids. Enhancements in the performance of mid‐wave infrared (MWIR) focal plane arrays are demonstrated by monolithic integration of Si micropyramids with silicon‐platinum silicide Schottky barrier photodetectors. Finally, it is shown that Si micropyramidal arrays can be used to enhance light extraction and directionality of quantum sources and infrared scene projectors.