Identification of Surface Defect Candidates and their passivation in Strained-Layer Type-II Superlattices for Infrared Detectors

The InAs/GaSb and InAs/InAsSb type-II strain-layer superlattices (T2SLS) are of great importance and show great promise for mid-wave (MW, 3-5 ?m) and long-wave (LW, 8-12 ?m) infrared (IR) detectors for a variety of civil and military applications [1]. Current infrared technology continues to rely on bulk mercury cadmium telluride (MCT) and InSb [2, 3] and GaAs/AlGaAs quantum well (QW) [4]. While MCT detectors have very large quantum efficiency (>90%) and detectivity (ratio of signal voltage to noise voltage), they are still plagued by nonuniform growth defects and a very expensive CdZnTe substrate [5]. There has been significant progress on development of MCT on silicon substrates, but good performance has been limited to the MWIR band only. The InSb detectors do not cover the LWIR spectral range. The GaAs/AlGaAs QW material [4] benefits from mature III-V growth and processing capabilities, featuring commercially available, lattice-matched substrates for high-quality epitaxial growth. Relatively high values of thermally generated leakage current caused by electron tunneling between quantum wells limit the operating temperature of GaAs/AlGaAs QW-based devices to ~60 K. Moreover, due to polarization selection rules for electron photon interactions GaAs/AlGaAs QW material is insensitive to surface-normal incident IR radiation resulting in poor conversion quantum efficiency [4].