Suppressing spectral crosstalk in dual-band long- wavelength infrared photodetectors with monolithically integrated air-gapped distributed bragg reflectors

Antimonide-based type-II superlattices (T2SLs) have made possible the development of high-performance infrared cameras for use in a wide variety of thermal imaging applications, many of which could benefit from dual-band imaging. The performance of this material system has not reached its limits. One of the key issues in dual-band infrared photodetection is spectral crosstalk. In this paper, air-gapped distributed Bragg reflectors (DBRs) have been monolithically integrated between the two channels in long-/very long-wavelength dual-band InAs/InAs_1-xSb_x/AlAs_1-xSb_x-based T2SLs photodetectors to suppress the spectral crosstalk. This air-gapped DBR has achieved a significant spectral suppression in the 4.5-7.5 μ m photonic stopband while transmitting the optical wavelengths beyond 7.5 μ m, which is confirmed by theoretical calculations, numerical simulation, and experimental results.