HgCdTe photodetectors

HgCdTe, a variable bandgap alloy, discovered in the United Kingdom in 1959, encompassed wide spectral bands in the infrared (IR) region. At present, it is the most widely used variable gap semiconductor for IR photodetectors. The intent of this chapter is to concentrate on HgCdTe device approaches and technologies that are having the most impact today, mainly in photovoltaic detectors. Advances of backside-illuminated HgCdTe heterojunction photodiodes have enabled third-generation multispectral instruments for remote sensing applications and have led to the practicality of multiband IR focal plane array technology. This chapter also presents the research and development programs around the world on future trends in HgCdTe IR detector arrays and their competitors. The sophisticated physics associated with type II superlattices (T2SLs), starting at the beginning of the 1990s, gave a new impact and interest in the development of IR detector structures within academic and national laboratories. III-Vs offer similar performance to HgCdTe at an equivalent cutoff wavelength, but with a sizable penalty in operating temperature, due to the inherent difference in Shockley-Read-Hall lifetimes. The important advantages of T2SLs are the high quality, high uniformity, and stable nature of the material.