Effect of Barrier Layer on InAs/GaSb Type- II Superlattice nBn Detector

Abstract

In a barrier infrared detector (BIRD), the design of the barrier layer plays an important role in device performance. In InAs/GaSb Type-II superlattice (T2SL) detector with the nBn structure, AlGaSb is generally used as a barrier layer material. However, AlGaSb material has strain due to lattice mismatch with T2SL absorption layer, and it has a valence band offset (VBO) with the absorption layer in terms of band alignment. The feature of T2SL material is that it has flexible in the bandgap engineering. Therefore, T2SL material can be designed as barrier layer material. In this study, the electronic band structure of InAs/GaSb T2SL is calculated using 8-band k.p envelope method. In the nBn detector with a T2SL absorption layer, it compares the performance of the designed T2SL barrier layer and the AlGaSb barrier layer. Our study shows that T2SL barrier detectors reduced turn-on voltage by bringing the VBO close to zero. And since the lattice constant of the absorption layer and barrier layer are similar, the strain is decreased, improving the dark current density characteristic.