Comparison of n- and p-type quantum well infrared photodetectors

摘要

Abstract: Rapid progress in quantum well IR photodetectors (QWIPs) technology has made it possible to develop large format, and high uniformity QWIP focal plane arrays (FPAs) for IR imaging sensor applications. So far, all QWIP FPAs are made of n-type GaAs/AlGaAs material systems grown on GaAs substrates due to the maturity of this material system and excellent detector performance. However, due to quantum selection rules, normal incidence absorption is forbidden in n-type QWIPs. As a result, n-type QWIP FPAs are required to use dielectric or metal gratings to efficiently couple the IR radiation into the quantum wells under normal incidence illumination. On the other hand, normal incidence absorption is allowed in p-type QWIPs without using the grating couplers. This property makes p-type QWIPs potentially more attractive for large format FPA applications. This paper will review the recent development in both n-type and p-type QWIPs for mid-wavelength, long-wavelength and very long wavelength IR detections. The basic device physics, structures, and performance parameters such as dark current, spectral responsivity, and detectivity for both n-type and p-type QWIPs will be depicted. Finally, a comparison of the advantages and drawbacks of n-type and p-type QWIPs will also be given. !21