Room temperature operation of epitaxial lead-telluride detectors monolithically integrated on midinfrared filters

Abstract

Epitaxial PbTe midinfrared photodetectors are monolithically integrated on optical filter structures, like λ∕4 antireflection layers or λ∕2 microcavities. The antireflection layers result in an increased photoresponsivity of the detectors by a factor of 2.2, measured at the target wavelength of 3.1μm. The microcavities, acting as efficient narrow band filters, consist of two PbEuTe∕EuTe Bragg interference mirrors separated by a PbEuTe cavity layer. The photoresponse spectra of the detectors integrated with the microcavity filters exhibit a single resonance at 3.6μm with a relative line width of 2.7%. The narrow photoresponse peak is in coincidence with a molecular absorption line typical for nonaromatic aldehydes. For all devices room temperature operation is demonstrated either in photoconductive or in photovoltaic operation mode.