Demonstration of far-infrared GaAs/AlGaAs quantum well photodetectors for broadband wavelength detection

We discuss the realization of broadband wavelength detection by demonstrati ng the longest cutoff wavelength (lambda (c) = 28.6 mum) far-infrared GaAs/ AlGaAs quantum well infrared photodetectors (QWIPs). The responsivity is co mparable to that of mid-infrared GaAs/AlGaAs and InGaAs/GaAs QWIPs, with a responsivity of 0.265 A/W and detectivity of 3.4 x 10(9) cm.Hz(1/2)/W at th e peak wavelength of 26.9 mum at 4.2 K. Based on the temperature-dependent dark current and response results, it is expected that similar performance can be obtained at least up to 20 K. Several ways to expand the wavelength coverage are also addressed.