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Extending the wavelength response of short-wavelength infrared detectors (SWIR) to 2 μm and beyond offers a key enabling technology for Lidar, spectroscopy, and imaging applications. Lattice-matched InGaAs/GaAsSb type-II superlattices (T2SL) have demonstrated SWIR detection around 2 μm on a highly producible InP platform but are limited in further extending wavelength response out to 2.5 μm. Introducing strain between alternating periodic layers of the superlattice provide a means to further extend wavelength while maintaining a strain balance (net zero strain). Numerical modeling utilizing 8 band k.p simulations were studied to examine the impact of bandgap energy, quantum confinement, and strain on the effective bandgap, wavefunction overlap, and corresponding absorption strength. T2SL with 4.73 nm In0.52Ga0.48As and 4.5 nm GaAs0.48Sb0.52 demonstrate extended wavelength response with absorption coefficient ~1000 cm-1 around the cutoff wavelength and over most of the 2-2.5 μm range indicating efficient overlap between the wavefunctions and high quantum efficiency values. Effect of period thickness, and strain on absorption coefficient and effective bandgap is analyzed and compared with the lattice matched case. Devices were fabricated with the superlattice structure as the absorber layer (3 μm thick) in a p-i-n photodiode configuration. Dark current voltage characteristics were measured and compared with simulated results. Measured dark current values were comparable to those of lattice-matched InGaAs/GaAsSb type II superlattices without extensive device optimization. Simulated quantum efficiency results showed clear extended cutoff of 2.5 μm with high quantum efficiency values in the 1.4-2.1 μm spectral region and features that closely follow absorption spectra validating the suitability of the strainbalanced approach in reducing the effective bandgap values while maintain absorption strength.
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