Advances in type-II superlattice research at Fraunhofer IAF

Abstract

Current advances in type-II superlattice (T2SL) research at Fraunhofer IAF are elaborated on in this paper. First, the use of metastructures for quantum efficiency (QE) enhancement in the longwave infrared (LWIR) is presented. Finite element modelling results are reported on that suggest a potential for doubling of the QE at certain wavelengths with the investigated device structure. Next, characterisation results of midwave infrared (MIWR) InAs/InAsSb T2SL nBn detectors are shown. The low, diffusion-limited dark current above 120 K and a QE of 60% are comparable to the state-of-the-art. Finally, groundwork for InAs/GaSb T2SL MWIR/LWIR dual-band detector arrays based on a back-to-back heterojunction diode device concept is presented. The dry etching technology allows for steep etch trenches and full pixel reticulation with a fill factor of about 70% at 12 µm pitch. The detector characterisation at 77 K and ±250 mV bias demonstrates the bias-switchable operation mode with dark current densities of 6.1·10−9 A/cm² in the MWIR and 5.3·10−4 A/cm² in the LWIR.