There is a number of photodetector types for light detection in the near, middle and long-wavelength infrared spectral ranges (NIR, MIR and LWIR). This variety of semiconductor photodetectors based on the effect of charge carriers generated by absorption of light (quantum photodetectors) are developed and used here.
The applications of such detectors are numerous, from the industrial control, scientific research, environment, and security to military and airspace applications.
The necessity of cooling and thermal stabilization for the detectors is due to the common property of semiconductors - a significant temperature dependence of physical properties of semiconductors and parameters of photodetectors based on them:
Different methods of thermal management are used for photodetectors. Among them, thermoelectric cooling is widespread and has its own advantages: miniature design, long-term durability, performance, no moving parts, no vibration.
PbS and PbSe Photodetectors
This is a class of widely used photodetectors in different fields from household, scientific applications, military and aerospace applications.
There are PbS and PbSe photodiodes, but till now the most common are the PbS and PbSe photoresistors.
They are so widely used due to a relative low cost and relatively simple manufacturing technique, at sufficiently high performance and reliability parameters. In many cases, the choice of these detectors is a compromise of optimal price/quality. Compared to higher performance but significantly more expensive detectors based on InSb and MCT, this class of detectors has the best price/quality ratio for a wide range of applications.
Although uncooled PbSe and PbS detectors are also used, the application of thermoelectric cooling increases their performance considerably for many special applications.
To provide high performance of PbS and PbSe Photodetectors single- and two-stage TECs are used. They provide required cooling to -20...-50°C temperature level, which is enough to provide a high performance of photodetectors.
There are two sub classes of photodetectors based on HgCdTe (MCT – Mercury Cadmium Telluride): detectors for spectral range 8-14 μm and 3-5 µm spectral ranges. For long wavelength spectral range MCT detectors deep cryogenic cooling to 100K and below is required. That is not possible with any state-of-art TECs.
In many practical applications Stirling cryogenic machines are used. In laboratory applications the simplest way for deep cooling - use of liquid nitrogen cryostats.
For MCT photodetectors of mid-infrared spectral range (3-5 µm range) cooling to -40…-70°C is sufficient to provide a normal operation. Such temperature conditions are provided by multistage design TECs – three- and four-stage TECs.
In the middle infrared (MIR) spectral range, particularly for 3-5 um wavelengths, InSb infrared p–i–n photodetectors are successfully competed with PbS and PbSe photodetectors and MCT Photodetectors.
This type of photodetectors is less expensive than MCT photodetectors but has significantly better performance parameters than cheap PbS and PbSe photodetectors.
InSb photodetectors require cooling for normal operation. Requirements of thermal management and operational temperature conditions are very similar to MCT photodetectors of the same Middle-IR spectral range.
Thus the similar solutions with multistage thermoelectric cooling to provide operational temperature conditions of -40…-70°C are needed.
To select a suitable solution and the optimal TEC for various photodetector applications, the supporting is available at RMT’s website. For detailed modeling and calculations the company RMT provides our customers by free software or .And for advice and assistance.