Quantum-Well, Infrared Photodetectors Using III-V Materialsp

Quantum Well Infrared Photodetectors (QWIPs) based on the III-V material system make an excellent detector choice for certain infrared applications. Although the QWIP does not compare favorably with the ideal HgCdTe detector due to its intrinsically shorter carrier lifetimes (about 1-10 ps) leading to large thermal generation rates, it does benefit from the more mature III-V epitaxial growth technology which allows better control and uniformity. In particular, for applications such as NASA's Earth Observation Satellite (EOS), which contains the Atmospheric Infrared Sounder (AIRS), the QWIP provides an ideal choice for the 12-16 micron region. The high Hg content required for operation in this region results in reproducibility difficulties as well as excessive dark currents. The high noise requires the additional expense of a space qualified chopper and associated differential amplifiers for each of the array elements. Although much work has been reported on the GaAs/AlGaAs based QWIP, the InGaAs/GaAs version will yield improved performance. The higher carrier mobility and lower effective mass associated with the InGaAs well and GaAs barriers will yield significantly enhanced response.