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The performance of Type II Strained Layer Superlattices (SLSs), incorporating III-V semiconductor materials, in infrared (IR) detectors and focal plane arrays (FPAs) is limited by the presence of surface leakage current. This phenomenon occurs in vertical mesa devices due to surface Fermi-level ‘pin’-ing of the p-type region in detectors built using a pn diode architecture. This is currently mitigated using a unipolar barrier architecture using n-type layers (nBn). Surface passivation of the p-type region in a pn diode via the p-type doping of mesa sidewalls with zinc as the dopant may invert the surface ‘pin’-ing, which may result in reduced leakage current. To properly identify whether this is possible, it must first be proven that the zinc compounds in question can indeed convert n-type SLS to p-type. The simplest way to confirm this is to create simplified homojunction planar diodes using thermal diffusion of zinc into n-type SLS. Thus, this study focused on a new fabrication process for simplified homojunction planar diodes. These planar devices were created using various techniques of zinc deposition and thermal diffusion to create p-type regions within n-type Type II SLS material. Electrical measurements of said devices have been compared to control devices, which consists of an electron blocking barrier to mitigate the surface leakage current. The preliminary results show promising dark current characteristics for several batches of pn diodes. This includes a rectification of 6 orders of magnitude for mid-wave infrared (MWIR) diodes and at least 2 orders of magnitude for long-wave infrared (LWIR) diodes. A detailed analysis of dark current characteristics, along with the spectral response of test devices, will be presented.
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