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dc.contributor.advisorQing Hu.en_US
dc.contributor.authorKonistis, Konstantinos, 1973-en_US
dc.contributor.otherMassachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.en_US
dc.date.accessioned2005-09-27T17:55:47Z
dc.date.available2005-09-27T17:55:47Z
dc.date.copyright2004en_US
dc.date.issued2004en_US
dc.identifier.urihttp://hdl.handle.net/1721.1/28712
dc.descriptionThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.en_US
dc.descriptionIncludes bibliographical references (p. 117-126).en_US
dc.description.abstract(cont.) features but the device self-heating turned out to be crucial for the longevity of the base micro-airbridges. The short lifetime of the base micro-airbridges was prohibitive for the realization of high frequency measurements. This work serves as the foundation for the implementation of robust HBT transit-time oscillators with the incorporation of slight modifications in the fabrication process.en_US
dc.description.abstractThis thesis explores the potential benefits of a GaAs-based heterojunction bipolar transistor (HBT) with stepwise alloy-graded base. The step height is slightly greater than the longitidinal optical (LO) phonon energy h[omega]LO in order to facilitate LO-phonon-enhanced forward diffusion of minority carriers in the base. The intuitive theoretical approach of carrier transport in the base, as proposed by other workers for this type of alloy-grading, did not incorporate in detail the various mechanisms of transport. In this work, we solved the Botzmann transport equation (BTE) in one dimension across the base for arbritrary frequencies. Impurity and LO phonon scattering were considered as the dominant scattering mechanisms. The intrinsic and extrinsic elements were combined and a small-signal equivalent circuit was proposed for the evaluation of the high-frequency performance of the device. The unique feature of this HBT is that the base transport factor undergoes a moderate magnitude attenuation and phase delay. By choosing a suitable collector delay, a band-limited negative output resistance can emerge in the microwave/millimeter-wave regime. The main benefit of the device is its inherent property as a transit-time high-frequency oscillator. Using our device simulator, we selected the material parameters for epitaxial growth (MBE) of the device wafer and we investigated various device layouts. We implemented the complete microfabrication of 2 [micro]m x 15 [micro]m, self-aligned, emitter-up HBTs with micro-airbridges for device isolation purposes. We performed DC measurements of various devices and they provided us with feedback for modifications in the MBE design and growth conditions of the device wafer. We finally fabricated HBTs with favorable DCen_US
dc.description.statementofresponsibilityby Konstantinos Konistis.en_US
dc.format.extent126 p.en_US
dc.format.extent7006227 bytes
dc.format.extent7022058 bytes
dc.format.mimetypeapplication/pdf
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsM.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582
dc.subjectElectrical Engineering and Computer Science.en_US
dc.titleA heterojunction bipolar transistor with stepwise allog-graded base : analysis, design, fabrication, and characterizationen_US
dc.typeThesisen_US
dc.description.degreePh.D.en_US
dc.contributor.departmentMassachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.en_US
dc.identifier.oclc59552651en_US


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