ABSTRACT
Since the initial proposal by Esaki and Tsu1 and the advent of MBE, the interest in semiconductor superlattices (SLs) and quantum well structures has increased continuously over the years, driven by technological challenges, new physical concepts and phenomena as well as promising applications. A new class of materials and heterojunctions with unique electronic and optical properties has been developed. Here we focus on devices which involve infrared excitation of carriers in quantum wells. A distinguishing feature of these infrared detectors is that they can be implemented in chemically stable wide bandgap materials, as a result of the used of intraband processes. On account of this, it is possible to use such material systems as GaAs/Al^Gaj^As (GaAs/AlGaAs), In^-Ga^As/ InxAli_xAs (InGaAs/InAlAs), InSb/InAsi_YSb^ (InSb/InAsSb), InAs/Gai-Jn^Sb (InAs/GalnSb), and Sii_xGe /^Si (SiGe/Si), as well as other systems, although most of the experimental works have been carried out with AlGaAs. Some of devices are sufficiently advanced that there exists the possibility of their incor poration in high-performance integrated circuits. High uniformity of epitaxial growth over large areas shows promise for the production of large area twodimensional arrays. In addition, flexibility associated with control over compo sition during epitaxial growth can be used to tailor the response of quantum well infrared detectors to particular infrared bands or multiple bands.
