Infrared focal plane arrays

Silicon is the material on which all matrix detector technology in the visible range (between 0.4 and 0.8 μm wavelength) is based. It is used both to absorb light and to process the resulting electrical signal. To date, the CMOS (Complementary Metal-Oxide Semiconductor) readout architecture has become the preferred choice for consumer applications, although the CCD (Charge Coupled Device) architecture is still used for certain applications such as astronomy. Matrix detectors for the visible range are commonly available in formats larger than megapixel (10 ³ × 10 ³ pixels). It is even possible to go up to a hundred megapixels without splicing (10 ⁴ × 10 ⁴ pixels) and up to a gigapixel (10 ⁹ pixels) by splicing several arrays together.

In the infrared range, it is no longer possible to use silicon as an absorbing material. Its bandgap energy is 1.12 eV at room temperature, making it impossible to absorb wavelengths greater than 1.11 μm. So we have to turn to other materials. There is no shortage of candidate semiconductors, and as a result, there are numerous infrared technology chains. So, with each new development, the infrared camera designer must ask himself the question of which detector technology he will choose, bearing in mind that this choice will influence the camera's performance (sensitivity, resolution, range, etc.), its characteristics (volume, mass, power consumption, etc.) and its implementation (possible need for cryogenics, calibration refresh rate, etc.). The aim of this article is to provide the reader with the information needed to make an informed choice of infrared detector for passive imaging applications. We do not deal here with the case of active imaging, which requires the use of a pulsed laser combined with a specific detector.

In paragraph 1 , we begin with some general information about infrared and the physics of detection in this spectral range. In paragraphs ...