High Temperature Ultra-High Performance MWIR/LWIR Detectors Based on Plasmonic-Enhanced Type II Superlattices

For ultra-high-performance IR detectors the only viable choice is HgCdTe or III-V type II SL based detectors. III-V is preferred over HgCdTe due to cost and a commercial supply chain. However, for LWIR HgCdTe still has superior performance. Performance can be improved either via material improvements (lifetimes) or through new designs. Performance of uncooled conventional MWIR/LWIR photodiodes are limited by the detectors’ dark current. Dark current scales with the detector volume, V; dark current noise scales as Sqrt V; and D* scales as 1/sqrt V. We propose to develop a MWIR/LWIR detector with an ultra-thin type-II superlattice absorber illuminated at a high intensity by a newly discovered surface plasmon polariton (SPP) mode produced by a grating etched into a highly-doped InAs layer. Unlike typical SPP modes that focus the intensity of incident electromagnetic waves approximately equally at the metallic and dielectric layers, this new mode focuses the intensity almost entirely at the dielectric layer where the absorber is located. The desired extent of coupling between the absorber and the new SPP mode can be achieved by optimizing the doping concentration of the InAs layer and the geometry of the etched grating. Photodiodes developed in this program will use plasmonic concentration to enable reduction of detector volumes by 104 – 105 x improving D* by ≥ 100. Such photodiodes will no longer be dark-current-limited, instead being limited by background radiation. In Phase I we will; model the SPP mode to optimize geometry of the grating and thickness of the InAsSb layer; Grow, fabricate, and measure structures to verify predictions of the model; Model the nBn T2SL candidate structures to find design for matching to the depth and wavelength of the SPP mode; Grow, fabricate and test nBn T2SL detectors without an etched grating to verify design. In Phase II we will develop designs and devices and deliver prototype high operating temperature MWIR and LWIR FPA’s.