Quantum efficiency and spatial noise tradeoffs for III–V focal plane arrays

Recent advances in quantum well detector materials such as SLS, QWIP, and QDIP photodetectors have made the performance of those technologies competitive with traditional MCT and InSb detectors while offering the potential of lower unit costs. Some III–V focal plane arrays operating in the MWIR spectral region have already achieved similar quantum efficiency performance as MCT and InSb devices, and are therefore, highly competitive for those applications. In the LWIR spectral region, quantum efficiency performance for III–V FPAs still lags MCT devices by a significant margin, but recent improvements have begun to close this gap. In addition, the improved spatial noise and operability typically associated with III–V devices can mitigate some of the shortfall in quantum efficiency when assessing overall system level performance. This paper will seek to quantify this tradeoff based on the most recent reported results for both III–V and MCT devices in order to help focus future research. This paper will first seek to quantify the current state of MCT and III–V (primarily SLS) FPAs in both MWIR and LWIR using a detailed literature survey to assess recent results, particularly in terms of reported quantum efficiency and spatial noise (quantified as residual fixed pattern noise). This data is then used to bound system-level performance modeling using the US Army’s Night Vision Integrated Performance Model (NV-IPM), which calculates image contrast and spatial frequency content using data from the target/background, intervening atmosphere, and system components. The modeling analyzes various tradeoffs in quantum efficiency and spatial noise under relevant operating conditions, including scenarios with both high and low target photon fluxes, and using realistic constraints for integration time (based on both frame rate and ROIC parameters). The results of this analysis are then compared to the current state of the art performance for both III–V and MCT FPAs to determine relative performance between the material systems and to recommend areas of improvement for each. This will provide insights to the FPA development community regarding the most pressing needs for improvements to each material system.