Fig. 1. Modular conduction band structure of the VLWIR QCD. The entire structure is based on the In_0.53Ga_0.47As/In_0.52Al_0.48As material system. The thicknesses of the layers in one stage are W1 (7.0), 2, 3.95, 5, 4, 4.5, 4, 4.3, 4.3, 1.95, 4.6, 3.5, 5, and 5 nm, where the underlined values correspond to absorption transition well (W1) and the bold numbers correspond to the In_0.53Ga_0.47As layer. Inset: detection wavelength as a function of the W1 well width.

Fig. 2. DME and extraction efficiency of devices at various well widths (W1). The green, blue, and red marker points correspond to the three experimental samples with different well widths below.

Fig. 3. XRD rocking curves of three QCD samples.

Fig. 4. (a) Normalized photocurrent spectra of three samples at 10 K and (b) their peak responsivity at different temperatures.

Fig. 5. (a) Differential resistance-area product R₀A and (b) detectivity of three samples as a function of temperature.