Pyroelectric films synthesized by low-temperatures and laser-processed for uncooled infrared detector applications

Infrared (IR) photon detectors based on III-V semiconductor quantum structures such as type-II superlattices [1] and quantum well infrared photodetectors (QWIPs) [2] require atomically flat interfaces, which are achieved through expensive, high-vacuum growth techniques such as molecular beam epitaxy (MBE). These structures are fabricated into detector arrays which are bump-bonded to Silicon (Si) Read-Out Integrated Circuits (ROICs). IR detector applications involving high resolution and fast refresh rates use highly sensitive photon detectors which require external cooling; making them bulky, expensive, and therefore impractical for equipping each soldier on the battlefield [3]. Uncooled thermal detectors tend to be lower cost, but the challenge is in developing materials that are thermally compatible with Si readout electronics. Thermal detectors convert incident radiation to heat. When a pyroelectric material is subjected to a temperature change, a dipole is induced, which sets up an electric potential. The resulting pyroelectric current can be read by the Si electronics. IR detectors based on perovskite oxides such as Barium Titanate (BaTiO3) are of interest in part because of their lack of need for cryogenic cooling, which makes them relatively more affordable and operationally simpler than cooled photon detector systems. Using a biologically-inspired low-temperature nanoparticle deposition technique, direct-write laser phase conversion, and micro-electro-mechanical systems (MEMS) fabrication techniques, we are working towards an uncooled IR focal plane array (FPA) process compatible with monolithic integration of the detector pixels directly onto ROICs.