Type of Document Dissertation Author Piyankarage, Viraj Vishwakantha Jayaweera Author's Email Address viraj@phy-astr.gsu.edu URN etd-02262009-124423 Title UNCOOLED INFRARED PHOTON DETECTION CONCEPTS AND DEVICES Degree Ph.D. Department Physics and Astronomy Advisory Committee
Advisor Name Title A. G. Unil Perera Committee Chair Brian D. Thoms Committee Member Douglas Gies Committee Member Kirthi Tennakone Committee Member Vadym M. Apalkov Committee Member Xiaochun He Committee Member Keywords
- CuSCN
- PbS
- Homojunction
- Heterojunction
- Workfunction
- Photoemission
- Displacement currents
- 1/f noise
- TiO2
- AlGaAs
- GaAs
- Dye-sensitized
- IR dye
- Quantum dot
- Split-off band
- GaSb
- THz detectors
- Uncooled detectors
- Infrared detectors
- Photon detection
- NIR detectors
Date of Defense 2008-10-28 Availability unrestricted Abstract This work describes infrared (IR) photon detector techniques based on novel semiconductor device concepts and detector designs. The aim of the investigation was to examine alternative IR detection concepts with a view to resolve some of the issues of existing IR detectors such as operating temperature and response range. Systems were fabricated to demonstrate the following IR detection concepts and determine detector parameters: (i) Near-infrared (NIR) detection based on dye-sensitization of nanostructured semiconductors, (ii) Displacement currents in semiconductor quantum dots (QDs) embedded dielectric media, (iii) Split-off band transitions in GaAs/AlGaAs heterojunction interfacial workfunction internal photoemission (HEIWIP) detectors. A far-infrared detector based on GaSb homojunction interfacial workfunction internal photoemission (HIWIP) structure is also discussed. Device concepts, detector structures, and experimental results discussed in the text are summarized below.Dye-sensitized (DS) detector structures consisting of n-TiO2/Dye/p-CuSCN heterostructures with several IR-sensitive dyes showed response peaks at 808, 812, 858, 866, 876, and 1056 nm at room temperature. The peak specific detectivity (D*) was 9.5E+10 Jones at 812 nm at room temperature.
Radiation induced carrier generation alters the electronic polarizability of QDs provided the quenching of excitation is suppressed by separation of the QDs. A device constructed to illustrate this concept by embedding PbS QDs in paraffin wax showed a peak D* of 3E+8 Jones at ~540 nm at ambient temperature.
A typical HEIWIP/HIWIP detector structures consist of single (or multiple) period(s) of doped emitter(s) and undoped barrier(s) which are sandwiched between two highly doped contact layers. A p-GaAs/AlGaAs HEIWIP structure showed enhanced absorption in NIR range due to heavy/light-hole band to split-off band transitions and leading to the development of GaAs based uncooled sensors for IR detection in the 2 5 μm wavelength range with a peak D* of 6.8E+5 Jones.
A HIWIP detector based on p-GaSb/GaSb showed a free carrier response threshold wavelength at 97 µm (~3 THz)with a peak D* of 5.7E+11 Jones at 36 μm and 4.9 K. In this detector, a bolometric type response in the 97 - 200 µm (3-1.5 THz) range was also observed.
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