Plasma Treatment for Surface Stabilization in InAs/GaSb Type-II Superlattice LWIR and VLWIR Photodetectors

An InAs/GaSb nBn structure was investigated as a replacement for mercury cadmium telluride (MCT) in long-wavelength infrared (LWIR) and very long-wavelength infrared (VLWIR) detectors, which is advantageous for detection of low-temperature objects. In antimony (Sb)-based III-V compounds, native oxides are easily generated during the process, and these contribute to the surface leakage current. Therefore, a key factor determining device performance is ensuring that native oxides are minimized and the surface is stabilized. Various wet solution-based treatments have been studied. Although wet treatments are effective for surface stabilization, native oxides can be regenerated by subsequent exposure to air or water. In this work, plasma treatments were investigated as an alternative to wet treatment. It was found that hydrogen (H₂) plasma treatment effectively reduced the native oxides, and trifluoromethane (CHF₃) plasma treatment inhibited the regeneration of the native oxides by coated polytetrafluoroethylene (PTFE) film. The LWIR and VLWIR devices fabricated with these plasma treatments exhibited a dark current density close to MCT rule 07. The proposed plasma treatments could be useful for enhancing the performance of type-II superlattice (T2SL)-based LWIR and VLWIR detectors.