Demonstration of Far-Infrared GaAs/AlGaAs Quantum Well Photodetectors for Broadband Wavelength Detection

We discuss the realization of broadband wavelength detection by demonstrating the longest cutoff wavelength (λ_c = 28.6 μm) far-infrared GaAs/AIGaAs quantum well infrared photodetectors (QWIPs). The responsivity is comparable to that of mid-infrared GaAs/AIGaAs and InGaAs/GaAs QWIPs, with a responsivity of 0.265 A/W and detectivity of 3.4x10⁹ cm.Hz^1/2/W at the peak wavelength of 26.9μm at 4.2K. 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.