Ultra-fast mid-infrared electro-absorption modulation in type-II InAs/GaSb multiple-quantum-well heterostructures for optical neuromorphic nodes: A self-consistent eight-band k˙p study

Photonic neuromorphic hardware requires modulators that combine fast response, low switching energy, and a well-defined activation nonlinearity. The mid-infrared window, which contains molecular absorption and supports low-loss free-space links, remains underexplored for interband electroabsorption modulation. We investigate strained type-II InAs/GaSb multiple quantum-well heterostructures as mid-infrared modulators and threshold elements. A zone-center-exact eight-band k⋅p Hamiltonian with Pikus–Bir deformation potentials and axial in-plane dispersion is solved together with Poisson's equation. Strain is prescribed through the common in-plane lattice constant, retaining the native tensile strain of InAs on GaSb while allowing both strain signs to be studied independently of alloy chemistry. Biaxial strain shifts the absorption edge across the mid-infrared window, whereas differential absorption varies weakly and exhibits no sharp strain optimum. The field-induced reduction of the lowest electron–hole overlap is compensated by a dense ladder of transitions in the broken-gap structure, limiting modulation contrast and bringing it closer to that of a type-I reference computed with the same solver. Strain, therefore, functions as a wavelength control parameter rather than a contrast control mechanism. Device-level analysis predicts voltage driven modulation with circuit-limited operation, while the field-dependent absorption produces a transient overshoot followed by a finite settling time. The transmission-charge characteristic is mapped onto a leaky-integrate-and-fire activation without parameter fitting for a mid-infrared photonic neuromorphic node. The results provide design guidance for strain programmable type-II electroabsorption modulators.