The rationale for ultra-small pitch IR systems

摘要

Large area high density vertically integrated (HDVIP) HgCdTe mid-wave infrared (MWIR) and longwave infrared (LWIR) focal plane arrays (FPAs) are now available with a 5um pitch, and excellent performance with regard to noise equivalent temperature difference (NETD), pixel operability, and modulation transfer function (MTF). This analysis examines the potential benefits provided by ultra-small pitch FPAs, not just on the resulting reduction in system size, weight, and power (SWAP), but also on the enabled improvement in system performance under extreme operating conditions, such as high operating temperatures. This potential performance strongly depends on the magnitude of dark currents associated with the chosen FPA detector architectures and materials technologies, and this analysis compares the limitations of prevailing HgCdTe photodiode architectures with today's III-V barrier layer photoconductors, not only with regard to the current marketplace, but also with regard to achieving the ultimate end-goal of background and diffraction limited MWIR and LWIR FPA performance at room temperature. Such a goal also imposes severe requirements on many other aspects of IR FPA technology, such as unit cell well capacity, and the development of pixel delineation and hybridization technologies to achieve a sufficiently adequate MTF for the ultra-small pitches involved. The challenges associated with these topics will be discussed.