Investigation of Superlattice Surface Characteristics

This research will remove the major obstacle to realizing the full potential of infrared (IR) photodetectors using strained-layer superlattice (SLS) absorbers. Modeling of the SLS surfaces will be performed by the simultaneous solution of the Poisson and Schroedinger equations. This will yield the surface characteristics and conductivity types of selected SLS structures. Growth of SLS structures will be performed by molecular beam epitaxy. Crystal quality will be assessed with X-ray diffraction, photoluminescence, and atomic force microscopy. Interface quality will be assessed with transmission electron microscopy. Processing of complete IR photodetectors with SLS absorber regions will be performed using standard photolithography techniques. Device performance will be assessed with temperature-dependent current-voltage characteristics, surface conductivity measurements, and calibrated photocurrent response measurements. This research addresses one of the requirements of TABS element 8.1.1, that of large focal-plane array detectors with low noise. It addresses this requirement by investigating the surface characteristics of SLS structures in order to design a detector that correctly suppresses surface leakage currents. By combining the unipolar barrier with an SLS absorber, an IR detector can be created with high QE, suppressed band-to-band tunneling, reduced Auger generation, and an arbitrarily long cutoff wavelength.

By combining the unipolar barrier with an SLS absorber, an IR detector can be created with high QE, suppressed band-to-band tunneling, reduced Auger generation, and an arbitrarily long cutoff wavelength.

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