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Design and Analysis of a Multicolor Quantum Well Infrared Photodetector

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Master's thesis

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Recent military applications have demanded photodetectors with high sensitivity, high selectivity and multispectral capability for detection and identification of the target. These characteristics have been found in quantum well infrared photodetectors QWIP. Driven by these applications, a QWIP photodetector capable of detecting simultaneously infrared emissions within near infrared NIR, mid wavelength infrared MWIR and long wavelength infrared LWIR was studied, modeled, designed and characterized. Using the envelope function approximation, the mathematical model of the quantum phenomena in semiconductor heterostructures was derived. A computational tool was developed to solve self-consistently the Schodinger-Poisson equation using the shooting method, allowing the theoretical evaluation of the absorption coefficient. A three-color NIR, MWIR and LWIR GaAs-based QWIP sample and a two-color NIR and MWIR InP-based QWIP sample were designed, both comprised of stacks of uncoupled wells for each band detection. The 67 layers of the GaAs sample was grown using molecular beam epitaxy MBE. Intersubband absorption in the sample was measured for the MWIR and LWIR using Fourier transform spectroscopy FTIR and the measured peak positions, found at 5.3 m , 8.7 m , and 13.8 m are within 0.3 m of the theoretical values, indicating that the model accurately predicts the absorption wavelengths. A twodimensional ordered grating pattern was selected and optimized separately for both MWIR and LWIR desired peaks. Finally the photodetector device configurations were designed to permit to the measurement of the NIR band through photocurrent spectroscopy and performance analysis. The fabrication and characterization of the prototypes are a matter for future work.

Subject Categories:

  • Electrooptical and Optoelectronic Devices
  • Infrared Detection and Detectors

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