Detectivity enhancement by double radiation pass in interband cascade infrared photodetectors

Abstract

The detectivity enhancement in a double-pass architecture in an interband cascade infrared photodetector (ICIP) is investigated. The ICIP consists of twelve identically thick absorbers composed of an InAs/GaSb type-II superlattice. To achieve a double-pass of radiation, a multilayer backside mirror was sputter-deposited after thinning the undoped GaSb substrate. At room temperature, a differential resistance area product of R0A= 1.37 Ω cm2 was achieved and the ICIP has a cutoff wavelength of 6.5 μm. By adding a backside mirror to the device, the responsivity was increased by 47% caused by the double radiation pass through the absorber. This resulted in a room temperature zero-bias detectivity of 8.3 × 108 Jones at a wavelength of 5.27 μm. Furthermore, oscillations are observed in the detectivity due to light interference from the reflected beam at the semiconductor/metal interface, which manifests the reflected double-pass device functionality unequivocally in the device characteristics.