<p>This master’s thesis deals with studies of lateral and vertical carrier transport Dot-in- </p><p>a-Well (DWELL) Quantum Dot Infrared Photodetectors (QDIPs). During the pro ject, </p><p>devices have been developed and tested using a Fourier Transform Infrared (FTIR) spec- </p><p>trometer with the purpose to find the processes governing the flow of photocurrent in </p><p>the different kinds of detectors, the dark current magnitude in the vertical Quantum Dot </p><p>Infrared Photodetector (QDIP) and the Quantum Well Infrared Photodetector (QWIP) </p><p>and the light polarization dependences for the vertical QDIP and the QWIP. </p><p>The lateral carrier transport DWELL QDIP was found to have poor conduction </p><p>in the well mainly due to re-trapping of electrons in this region. The main process gov- </p><p>erning the flow of photocurrent for this type of device at 77K is photo-excitation from </p><p>the Quantum Dot (QD)s to the excited state in the Quantum Well (QW) and further </p><p>thermal excitation. If the electrons are mainly transported in the matrix or the well at </p><p>77K is presently not clear. </p><p>For the vertical carrier transport DWELL QDIP at 77K, the wavelength response </p><p>could be tuned by altering the applied voltage. At higher voltages, the dominant process </p><p>was found to be photo-excitation from the QDs to the excited state in the QW followed </p><p>by thermal assisted tunneling into the GaAs-matrix. At lower voltages, photo-excitation </p><p>from the QDs directly into the the GaAs-matrix was the predominant process. The dark </p><p>current level in the vertical QDIPs was found to be 1.5 to 5 orders of magnitude smaller </p><p>than for the QWIP measured at 77K. Furthermore, the QDIP was found to be close to </p><p>polarization independent. As expected the QWIP had a reduced sensitivity to normal </p><p>incident light. The existence of this signal was attributed to interface scattering of light </p><p>inside the device.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:hh-234 |
| Date | January 2006 |
| Creators | Hansson, Conny, Kishore Rachavula, Krishna |
| Publisher | Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Högskolan i Halmstad/Sektionen för Informationsvetenskap, Data- och Elektroteknik (IDE) |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, text |
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