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High-temperature quantum dot infrared photodetector for mid-infrared and far-infrared wavelength ranges

Posted on:2007-02-19Degree:Ph.DType:Dissertation
University:University of MichiganCandidate:Su, XiaohuaFull Text:PDF
GTID:1448390005964055Subject:Engineering
Abstract/Summary:
Infrared detectors have a wide range of imaging applications, including medical diagnosis, thermal imaging, and night vision. A typical infrared camera includes a liquid-nitrogen cooling system. The cost of infrared cameras can be reduced significantly, and their weight can also be decreased, if these cooling systems are replaced by thermo-electric coolers, or completely removed. This necessitates that the detectors can operate at high temperatures (≥150K). Quantum dot infrared photodetectors (QDIPs), with three-dimensional confined quantum dots in the active regions, have the potential for high temperature operation. In the present study, QDIPs have been designed, fabricated and characterized. The results demonstrate that QDIPs have great potential for high temperature operation.; Quantum dot infrared photodetectors, with multiple In0.4Ga 0.6As/GaAs quantum dot layers in the active region have been investigated. The spectral response of these devices exhibits three wavelength absorption peaks, centered at 3.5, 7.5, and 22mum respectively. Good performance (J dark∼10-4A/cm2, Rpeak=0.15A/W, D*∼1010cm.Hz1/2/W, T=80K, Vbias=2.0V) was observed for a 30-dot layer device. The highest operating temperature of a 20-dot layer device is 120K while that of 30-dot layer device is 200K.; A novel QDIP, in which a resonant tunneling filter is incorporated with each quantum dot layer in the active region of the device, has been studied theoretically and experimentally. In this tunnel QDIP (T-QDIP) the double barrier resonant tunneling heterostructure selectively transmits the photoexcited carriers while blocking the carriers, with a broad energy distribution, which contribute to the dark current. A significant suppression of the dark current, by almost two orders of magnitude, is theoretically calculated and experimentally measured in these devices. Room temperature operation for a QDIP was demonstrated for the first time with the tunnel device with good performance (Rpeak=0.16A/W D*∼107cm.Hz 1/2/W, T=300K, Vbias=2.0V).; Terahertz detection with the tunnel QDIPs was also demonstrated for the first time with InAlAs/GaAs quantum dots in the active region. These devices show a long wavelength cut-off at ∼75mum (4THz) and high temperature operation (150K).
Keywords/Search Tags:Quantum dot infrared, Temperature, Wavelength, Active region, Device
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