High-Performance Midwave Type-II Superlattice Infrared Photodetectors With a Stepped InAs/GaSb Absorber

Due to the short carrier diffusion length, the extraction of photogenerated carriers is one of the key issues in InAs/GaSb superlattice (SL) photodetectors. Here, we report a midinfrared InAs/GaSb SL absorber with a stepped band alignment. The stepped absorber facilitates a better carrier extraction efficiency. Simulation results show that the proposed nBn detector with a stepped absorber exhibited a substantial performance improvement over the nBn detectors with uniform absorbers. At 150 K, the detector with a 3.6- $\mu \text{m}$ -thick stepped absorber has a maximum quantum efficiency (QE) of $\sim $ 46%, which is about 16% higher than that of the detectors with uniform absorbers. The maximum specific detectivity reached $\sim 4.26\times 10^{{10}}$ cm $\cdot $ Hz $^{\text {1/{2}}}$ /W at 4.9 $\mu \text{m}$ under −0.2 V bias. With the enhanced carrier extraction efficiency, the detectivity can gained a further improvement with a thicker stepped absorber, unlike the detector with a uniform absorber where the detectivity deteriorated with the absorber thickness increased from 3.6 to $4.2 \mu \text{m}$ .