Low Capacitance SWIR Photodetectors For High Speed Sensing Applications

Sensors Unlimited Inc., a Collins Aerospace Company, has advanced its high-speed short-wave infrared (SWIR) focal plane arrays (FPA) to meet increasing field-of-view (FOV) and bandwidth demands for LiDAR and imaging applications. By modifying its standard Indium Gallium Arsenide (InGaAs) photodiode arrays (PDA), including adjustments to junction shape, dielectric passivation design, hybridization bump shape, and contact metallization, SUI has significantly reduced total effective capacitance. These improvements, which cut capacitance load on the detector and readout integrated circuit (ROIC) by over 50%, enhance laser pulse detection while preserving the company’s industry-leading low dark current.

The modifications support both high-speed P-I-N photodiode and Avalanche Photo Diode (APD) arrays, enabling superior performance in low-light imaging, coded-pulse tracking, and laser range-finding applications. Additionally, the implementation of high-aspect-ratio bumps (HAR-bumps) minimizes capacitance by reducing metal area contact and optimizing the spacing between the PDA and ROIC, improving system efficiency.

These enhancements contribute to better detection sensitivity, crucial for long-distance light detection applications, by reducing system noise. SUI’s proprietary epitaxial structure ensures minimal dark current, maintaining low-noise performance. The resulting technology is well-suited for LiDAR systems, offering enhanced imaging capabilities and laser pulse tracking. The modifications can also be applied to bump-bonded 1D (linear) arrays. These advancements reinforce SUI’s position as a leader in SWIR sensor technology, optimizing high-speed photodetection for a range of optical applications.