MWIR pBn Unipolar Barrier Photodetectors Based on Strained Layer Superlattices

In recent years, unipolar barrier photodetectors have received a lot of attention due to their ability to achieve significantly lower levels of dark current than traditional structures. One of the most attractive material systems used in the development of unipolar barrier photodetectors is the InAs/GaSb Type II Strained layer Superlattice (T2SL). This material system provides the ability to engineer the band structure of the device, which can be exploited to make unipolar barriers. It has been shown that band-gap engineered unipolar barrier T2SL devices can obtain significantly lower levels of dark current than traditional homojunction T2SL devices. In this work, we present data on pBn unipolar barrier photodetectors based on the T2SL material system. These structures have been designed so that the cut-off wavelength is around 5 microns at 100 K. To accomplish the design goals we developed an EPM-Poisson solver (EPM: Empirical Pseudopotential Method) that calculates the band structure of the T2SL layers and the band alignment as a function of the doping profile. To evaluate the performance of the designed structure, we characterize the radiometric performance of single-pixel devices that we fabricate using a variable area mask. In this presentation, we compare the performance of the designed structure to other unipolar barrier designs and discuss its advantages and disadvantages.