RMS noise modeling and detection for high-reliability HgCdTe infrared focal plane arrays development

Abstract

This paper presents recent improvements introduced in production lines of Mid-Wavelength Infra-Red (MWIR) and Long-Wavelength Infra-Red (LWIR) HgCdTe detectors that increase performances, image quality, and reliability. This was achieved thanks to accurate characterization of RMS noise distributions. Based on many MWIR and LWIR devices RMS distributions, a RMS noise distribution model that accounts for both Background Limited diodes and 1/f noise affected isolated diodes is first proposed. Then, a figure of merit for quantifying the defective pixels is introduced. This figure of merit is shown to be easy to use and robust to statistical variability. Moreover, it does also very well correlate with physics : there is high correlation between the total number of calculated defects and other figures of merit that gauge the material quality or the low frequency noise. The ability to accurately and efficiently quantify RMS noise benefits to Sofradir in its development of highly reliable and performant technologies. Such benefits are illustrated on the latest Sofradir MWIR and LWIR technologies that are demonstrated to be very robust regarding thermal stress and thermal cycling. Finally those technologies are shown to reach high image quality and stability.

Low frequency noise in p-InAsSbP/n-InAs infrared photodiodes

“…Low frequency noise is an important characteristic of PDs. In particular, the high level of low frequency noise hinders the improvement of infrared detectors such as PbS, PbSe и CdHgTe [5][6][7][8]. Noise analysis is also a well-known tool to characterize the material quality and device reliability [9][10][11][12].…”

Application of cooled IR focal plane arrays in thermographic cameras

“…These large apertures ensure that the integration times can be short enough to measure rapid temperature changes or observe fast moving objects. Most of the state-of-the-art IR FPA detectors allow the reduction of the integration time by adjusting the effective integrating capacity [5][9][11] [12]. Indeed, the signal-to-noise ratio will be better if the same output signal response is reached by a large aperture than by a high gain of the charge voltage conversion.…”

“…MWIR FPAs are mostly long-term stable. Therefore, it is normally sufficient to correct the slow increase of their RFPN over time by an offset adjustment [2] [5], which can be easily performed with an internal or external shutter.…”

“…The integrated ADCs of these ROICs are typically assigned to the columns [5][9][10] [11]. Some digital ROIC architectures address all columns independently from the used frame size.…”