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Title: Acoustoelectric interactions in resonant tunnelling structures
Author: Hutchinson, A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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This thesis presents a novel device architecture allowing the monolithic integration of SAWs and semiconductors, which compensates for the inherent weakness of piezoelectric coupling in GaAs by relying on a strong non-local interaction mechanism. A special double-barrier quantum well RTS is designed so that large vertical currents can be sensitivity triggered by a small potential near the surface of the structure, such as the potential associated with a SAW. When a SAW beam is incident on the RTS mesa, the peaks ( and valleys) of the SAW electric field change the potential across the quantum well, resulting in local increases (and decreases) of the current through the structure. With the appropriate device design, the net effect of the SAW integrated over the entire RTS mesa will induce a microwave current in the receiving circuit connected to the RTS emitter. The basic linear and nonlinear properties of the microwave response have been investigated. Simple phenomenological models taking into account the spatial distribution of the SAW electric field and the nonlocality of the RTS conductivity have demonstrated good agreement with experimental results. The effect of varying the RTS layer structure on both the dc characteristics and the microwave response has been investigated theoretically, and experiments once again support the predictions. A process for non-annealed Ohmic contact to the RTS emitter has been optimized, in which Al is grown in situ on highly-doped GaAs incorporating several layers of δ-doping near the surface. The use of this contact method helps to eliminate the extrinsic instability observed in the negative differential resistance region of early devices. Finally, possible applications of the interaction are discussed, including a proposal for the parametric generation of very high frequency SAWs.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available