Quantum Dots Infrared Photodetectors (QDIP).

Abstract

Theoretical predictions show that thermal generation rate in quantum dots can be significantly smaller than in quantum wells, rendering a much improved signal to noise ratio. Quantum Dots Infrared Photodetectors (QDIP) were implemented in a GaAs/InAs material system. The device is composed of 10 layers of self assembled InAs dots grown on GaAs substrate. The illumination was introduced through a wedge in order to investigate polarization effects. A clear spectral response was obtained at 13K, with two peaks. The first, at 6.5 μm, is polarized parallel to the growth axis, and is attributed to excitation from the first confined level to the continuum. The second, centered around 15 μm, is unpolarized, and is due to excitation from the second confined level to the continuum. The fact that a photoconductive signal was recorded even though no absorbance was observed, indicates a very large gain due to a very long lifetime, consistent with theoretical predictions. It is estimated that once a device with quantum efficiency comparable to that of Quantum Well Infrared Photodetectors (QWIPs) is realized, it will be possible to operate QDIPs at temperatures higher than QWIPs.