ABSTRACT
The quantum well Infrared photodetector (QWIP) has been developed for long-wavelength infrared detection for nearly three decades. On the basis of the mature III–V GaAs material technology, QWIP focal plane array (FPA) cameras are readily available in commercial markets. These cameras are economical, and they offer high thermal sensitivity and good image quality. The technology has gained wide popularity in civilian applications, such as border security, gas sensing, and Earth observation. On the other hand, they are less employed in more demanding areas such as those in the military. Owing to their lower quantum efficiency (QE) and higher dark currents, QWIP FPAs tend to operate at lower speeds and temperatures than other technologies. In recent years, however, there has been a new development in detector optical designs, which can greatly mitigate these shortcomings. These new structures are designed through rigorous electromagnetic modeling to trap light more efficiently so that the QE can be larger. With a larger and more predictable QE, the QWIP technology is more capable and desirable in all areas of infrared detection. In this entry, we will describe the core operating principles of QWIPs and discuss the detector optimization for various applications.
