Fabrication of Tunable Quantum Well Infrared Photodetectors (QWIP), Polarization Sensitive QWIPs and Enhanced Coupling Grating Structures

摘要

This project investigates the properties of intersubband reduced dimension devices based on quantum wells and quantum dots, which could be used for infrared detection. In the past few years, there has been active research on studying the performance characteristics of mid-wave infrared (MWIR, 3-5 m) and long-wave infrared (LWIR, 8-12 m) applications. Present-day photon detectors in this wavelength range need to be cooled to liquid nitrogen temperature or below. Quantum dot detectors are expected to display low dark current, large detectivity and better response at elevated temperature due to the longer lifetime of excited electrons due to greatly suppressed electron- phonon scattering. The responsivity and specific detectivity of QDIPs is significantly lower than those observed in mercury cadmium telluride (MCT) detectors. However, due to difficulties with the epitaxial growth of mercury based compounds, material defects cause problems with uniformity and operability across an array that continues to plague MCT focal plane arrays. QDIPs, on the other hand, are based on a comparatively mature GaAs technology and the uniformity of their response suggests that they can be incorporated into large area focal plane arrays (FPAs).