MULTICOLOR INFRARED DETECTION USING STEP QUANTUM WELLS

Quantum well infrared photodetectors (QWIPs) based on intersubband transitions are widely investigated in recent years. Due to the mature III-V material and processing technology, great progress has been made successfully for the fabrication of large scale quantum well infrared focal plane arrays (FPA). In the meantime, various kinds of quantum well structures with novel properties are also explored. Multi-color detection, which may enhance the discrimination ability of infrared detectors, is one of the features that quantum well structures can offer. The intent of this dissertation is to achieve multicolor detection with a unique quantum well structure based on step quantum wells and superlattice batTiers. In order to study the subband structure and the intersubband transition in arbitrary shape quantum wells, a transfer matrix method with effective mass approximation has been constructed. The energy states and intersubband transitions are discussed theoretically with the help of this method. This method was used to design the detector structure with step quantum wells and superlattice barriers for multicolor detection. The sample was designed to have multicolor photoresponse by using bound-to-bound and bound-to-continuum intersubband transitions. The quantum well structure was composed of InxGa1-xAs, GaAs and AlyGa1-yAs layers. The sample was grown by molecular beam epitaxy (MBE) on (100) semi-insulating GaAs substrate.

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