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Heterojunction Structures for Photon Detector Applications

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Technical Report

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The work presented here report findings in 1 infrared detectors based on p-GaAsAlGaAs heterojunctions, 2 J and H aggregate sensitized heterojunctions for solar cell and photon detection applications, 3 heterojunctions sensitized with quantum dots as low cost solar energy conversion devices and near infrared photodetectors. 1 A GaAsAlGaAs based structure with a graded AlGaAs barrier is found to demonstrate a photovoltaic responsivity of approximately 30 microAW approximately 450mVW at the wavelength of 1.8 micron at 300K. Additionally the graded barrier has enhanced the photoconductive response at 78 K approximately 25 times improvement compared to the flat barrier detector structure, probably due to the improved carrier transport, and low recapture rate in the graded barrier structure. However, these graded barrier devices did not indicate a photoresponse with photoconductive mode at 300K due to high shot noise. Additionally, two generation-recombination noise components and a 1f noise component were identified. A series of GaAsAlGaAs multilayer hetero-junction structures were tested as thermal detectors. 2 The photovoltaic properties of heterojunctions with J- H- aggregated dye films sandwiched between n and p-type semiconductors were investigated for potential application as solar cells and IR detectors. Films of cationic dye Rhodamine-B-thiocyanate adsorbed on Cu2O substrate are found to form organized dye layers by self-assembled J- aggregation, resulting in large red-shifts in the photo -response. Additionally, cells sensitized with a pentamethine cyanine dye exhibited a broad spectral response originating from J- and H-aggregates. The photocurrent is produced by exciton transport over relatively long distances with significant hole-mobility as well as direct sensitized injection at the first interface. 3 A ZnOPbS-QDDye heterostructure had enhanced efficiency compared to ZnODye heterostructure as a solar cell.

Subject Categories:

  • Optics
  • Crystallography
  • Electric Power Production and Distribution

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