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oai:www.ideals.illinois.edu:2142/19926 2023-07-10 col_2142_5131 col_2142_8888 com_2142_5130 com_2142_8887 com_2142_234

Kushner, Mark J. Stout, Phillip J. 2011-05-07T12:23:06Z 2011-05-07T12:23:06Z 10000-01-01 1995 A two-dimensional time dependent computer model of a GaAs PCSS has been developed to investigate nonuniformities in the electric field observed in the operation of a high power photoconductive semiconductor switch. The model solves the continuity equations for electrons, holes, and traps, the energy equation for the lattice, Poisson's equation, and a circuit equation. Physical effects in the model include band-to-band impact ionization, trap impact ionization, photoionization, recombination radiation transport, and negative differential resistance. The model has the ability to address different switch geometries and the consequences of nonuniformities in carrier injection, permittivity, and illumination of the sample on switch operation. Results from modeling bulk and coplanar GaAs (Si:Cu) switches show that the switching cycle is sensitive to the type of laser spatial distribution, the trap doping levels, the circuit parameters, and the geometry of the device. Delivering light directly under the contacts decreases the voltage closing level. Intrinsic impact ionization is essential to closing the GaAs (Si:Cu) switch. For a coplanar switch with an ungrounded base, field enhancement occurs near the anode and cathode as the switch begins to close. This enhancement shifts to the cathode during the on state. When opened, an electric field enhancement front begins to migrate back toward the anode. The mobile front is a consequence of negative differential resistance. The spatial shape of laser penetration affects the shape of this field enhancement. For the ungrounded base, field enhancement occurs only near the anode during closing. In the opening stage a high field region forms near the anode inhibiting opening. As a result, opening is less sensitive to the opening laser pulse when a grounded base coplanar switch geometry is used. Band-to-band recombination radiation transport plays an important role in carrier transport when the switch is closed with a spatially nonuniform laser pulse. Reabsorption of the radiation ultimately reduces the electric field at the contacts, which allows the switch to close. The model predicts that the switch is sensitive to the location of the activating laser pulse. Less laser fluence is required to close the switch near the cathode than near the anode. Made available in DSpace on 2011-05-07T12:23:06Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9543735.pdf: 5901467 bytes, checksum: 56d2e06d0322ef1627ea03316edbb232 (MD5) Previous issue date: 1995 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:40:22Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:17:15-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission ETDs are only available to UIUC Users without author permission U of I Only AAI9543735 (UMI)AAI9543735 http://hdl.handle.net/2142/19926 eng Copyright 1995 Stout, Phillip J. Engineering, Electronics and Electrical Modeling optically activated high power semiconductor switches text Electrical and Computer Engineering Electrical Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.