Minority carrier diffusion length for electrons in an extended SWIR InAs/AlSb type-II superlattice photodiode

We fabricated and characterized InAs/AlSb Type II superlattice photodetectors for the short wave infrared region with λcutoff close to 2.5 μm. Using C-V and quantum efficiency measurements, we extracted the carrier diffusion lengths, Ldiff, and at 220 K and 300 K, they were 0.94 μm and 1.9 μm, respectively. In addition, I-V and detectivity measurements were carried out. The quantum efficiencies at λ = 2.18 μm, −50 mV, 300 K, and 200 K were 29% and 16% and the detectivities were above 1010 and 2 × 1011 cm Hz1/2/Watt, respectively. At a bias of −50 mV, the dark current densities at 300 K and 200 K were 4 mA/cm2 and 2.3 × 10−6 A/cm2 and the resistance-areas were 16 Ω cm2 and 38 kΩ cm2, respectively.