Charge carrier dynamics and optoelectronic properties in quantum tunneling heterostructures
Guarin Castro, Edgar David
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Semiconductor quantum tunneling heterostructures offer a wide range of applications as photosensors, lasers, and circuit elements. However, fundamental questions related to energy transfer mechanisms and the correlation between some electrical and optical responses remain challenging. In order to provide insights into these problems, the nature of the carrier dynamics in these structures has been investigated by exploring the role of majority and minority carriers in the optoelectronic responses and the limiting factors responsible for their modulation. Thus, the transport and optical properties of different n-type samples built on Sb- and As-based double-barrier quantum well architectures have been analyzed using transport measurements and luminescence spectroscopies in continuous- and pulsed-wave mode. The characterization has been carried out by tuning various external parameters such as temperature, illumination, and magnetic fields. Our observations revealed resonant tunneling of carriers from cryogenics up to room temperature. The inclusion of III-V quaternary alloys enhances the photodetection of infrared wavelengths. Quaternary layers serve as absorbers that allow a thorough tuning of the photosensor capabilities. The optical response of the devices allowed unveiling complex dynamics of non-equilibrium carriers, pointing out the formation of independent electron and hole populations that do not thermalize. This characteristic enables the mapping of thermalization mechanisms of hot carriers along with the structures. In all cases, it was found that the optoelectronic characteristics of the devices are strongly intertwined. In this regard, bistable optical and transport characteristics associated with an intrinsic magnetoresistance of some samples can be modulated simultaneously with temperature and magnetic fields. Models were proposed to simulate the charge dynamics, discerning the main ingredients that control the electrical response and, in some cases, the photosensor abilities. These models were complemented considering coherent and incoherent transport channels, which demonstrates how the transport and optical attributes correlate to produce the peculiar quantum response. This approach allows discussing the role of minority carriers in the overall dynamics of the systems, the segmentation of the relaxation mechanisms, and the optimization of the optoelectronic properties. The results are intended to offer a comprehensive theoretical and experimental analysis of the complex quantum phenomena behind these quantum tunneling systems.
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