Electron transport in quantum well infrared photodetectors

Citation

Shakouri, Ali (1996) Electron transport in quantum well infrared photodetectors. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/aqq2-yj56. https://resolver.caltech.edu/CaltechETD:etd-05172005-084805

Abstract

In this work the technique of molecular beam epitaxy is used to grow GaAs/AlGaAs multiquantum well structures. The material composition and thicknesses are chosen in a way that the electrons in the device interact resonantly with infrared radiation. This interaction originates from quantized energy states (subbands) in the conduction band of the material. The infrared absorption and photocurrent spectroscopies, in conjunction with standard DC-characterizations, are used to investigate electron transport in these structures.

After a brief description of electronic energy states based on the multi-band k.p approximation, the optical properties of intersubband transitions are theoretically and experimentally investigated. Evidence for the above-the-barrier energy states (continuum minibands) affecting the absorption and photocurrent spectra is presented.

Studying electron transport perpendicular to the multiquantum well layers, different regimes of miniband and hopping conduction are distinguished. It is shown that sequential resonant tunneling and electric field domain formation occur even in very weekly coupled quantum wells (separated by 44 nm barriers), its application to the design of voltage-controlled multi-color infrared detectors is discussed and demonstrated. Finally, the low bias behavior of quantum well detectors is analyzed and evidence for photocurrent flowing in the opposite direction to the applied bias is presented.

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