In recent years, due to the rapid development of infrared technology, the demand for infrared detectors in various fields has also become diverse. Requiring high performance devices while maintaining high operating temperature has always been the goal pursued by researchers.
By selecting high-performance materials, optimizing device structure, improving material growth and device technology, the working temperature of mid-wave infrared detectors (usually liquid nitrogen temperature) can be increased to a higher temperature (about 150 K), also known as HOT infrared detector.
The key technical approach of the HOT infrared detector is to reduce the dark current. It has higher reliability, lower cost, greater autonomy and smaller size than traditional mid-wave infrared detectors. The main problem of HOT infrared detectors is that higher operating temperature will cause more defects in existing materials and devices, resulting in greater low-frequency noise. Therefore, developing high-quality materials, mastering mature device process technologies (annealing, etching, surface passivation, flip-chip interconnection, etc.) and improving traditional processes are very important for the development of HOT infrared detectors. At present, a lot of research has been carried out at home and abroad on medium-wave HOT infrared detectors, including InAsSb detectors with nBn structure and HgCdTe detectors with thermoelectric cooling.
The materials used for infrared detectors mainly include InSb, HgCdTe, quantum wells and antimonide II superlattice. Most of the HgCdTe and InSb infrared detectors work at 77K. If the operating temperature of the device is increased, the dark current will increase exponentially, and the increase of the dark current will lead to a serious decline in the performance of infrared detectors.
In order to keep the device at a working temperature of 77K, a high-power cryo cooler is required, which not only leads to problems such as large system size, high power consumption, and limited life, but also brings a lot of inconvenience. Studies have shown that if the operating temperature of the detector can be increased by 20% to 30%, the life of the whole system will be extended by 50% to 150%.