Chapter 9 Conclusions, Trends, and Perspectives

Low-temperature electronics or cryoelectronics has traditionally been used for fundamental research on semiconductor materials. The electronic properties of semiconductors (carrier mobility and thermal conductivity) and the internal energy distribution in semiconductor crystals can be better understood when they are analyzed and measured at low temperatures. This information is useful for band gap engineering, when designing devices with tailored characteristics. Thus, cryoelectronics was first used as a powerful tool to investigate the physical properties of solid-state materials. Later, when the low-temperature properties of semiconductor materials were known and available, the development of low-temperature devices was begun. Devices such as photodetectors for mid- and far-infrared detection were first developed. These types of radiation detectors needed low-temperature operation because of the low-noise and long-wavelength detection requirements. The discovery of the superconductivity marked a new era for cryoelectronics because of the superconductivity and the practical and reliable cryocoolers, which were also used for applications in solid-state measurement instruments.