High performance LWIR detectors are highly needed. In order to image from long distance, it is important that imagers have high sensitivity, high resolution, and very low dark currents. This leads to technical goals of having low noise, low dark current in small size pixels in large arrays. While saturated performance levels of traditional systems based on bulk semiconductors have not quite met the requirement of applications, it is expected that novel quantum systems will bring new development stage for infrared imagers. In recent years, Type-II InAs/GaSb superlattice (T2SL) has experienced significant development, from theoretical modeling, material growth to device processing and packaging. Performance of LWIR detector based on T2SL has become comparable, even better than that of HgCdTe. However, LWIR T2SL devices have been shown to be limited by surface leakage, especially at lower operating temperature. This proposed effort will investigate gating of Type-II photodiodes as a means to suppress this bottle neck of T2SL technology. The ultimate goal of this project is to develop an effective method to completely suppress the surface leakage current in LWIR type-II superlattice photodiodes that is compatible with the development of high performance gated FPAs in Phase II.