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 m-thick stepped absorber has a maximum quantum efficiency (QE) of similar to 46%, which is about 16% higher than that of the detectors with uniform absorbers. The maximum specific detectivity reached similar to 4.26 x 10(10) cm center dot Hz(1/2)/W at 4.9 mu 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 m.