<i>α</i>/<i>G</i> figure of merit for infrared photodetector materials

In the last 20 years, we have witnessed enormous technological nanofabrication progress in the development of a new generation of infrared photodetectors. In this broad class of photodetectors, generally called low-dimensional solids (LDS), we can distinguish two-dimensional materials, perovskites, nanowires/quantum dots, and organic materials. They operate in a wide wavelength range from ultraviolet to far-infrared. However, our considerations are limited to the IR spectral range. A great number of papers have been published so far, including review papers, some of which predict an enthusiastic future for these photodetectors. One of the fundamental criteria for assessing the suitability of material used in the active region of an infrared photodetector is the α/G ratio, where α is the threshold absorption coefficient of the material and G is the thermal carrier generation rate. From carried out consideration follows that the square root of the absorption coefficient of the material and the carrier lifetime (ατ) can be used as a criterion for the quality of the infrared material. In this study, we use this criterion to compare the suitability of different groups of new-generation materials potentially competing with standard materials dominating the commercial global market. Before that, however, the basic differences in the photoelectric properties of LDS materials compared to standard materials are explained. Particular attention was paid to the influence of basic material properties (absorption coefficients, carrier lifetimes, and carrier mobility) on the performance of infrared photodetectors. Since HgCdTe occupies a dominant position among the latter, this ternary alloy system is the reference material. It has been shown that it will be difficult for LDS photodetectors to compete with HgCdTe photodiodes.