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Breakdown studies of high-voltage silicon and gallium arsenide photoconductive switches
Abstract
Silicon and gallium arsenide photoconductive switches are attractive choices for pulsed power applications which require low jitter, high speed operation. However, both of these materials exhibit breakdown modes which limit optical system efficiency. Experimental results are presented on surface breakdown of high resistivity silicon in vacuum. Breakdown characteristics were measured for electric fields between 15 and 50 kV/cm across 1 cm silicon devices with heavily doped contacts in a parallel plate geometry. The first current rise signaling breakdown developed in as little as 25 ns after the field was applied. Simultaneous high gain streak and shutter photography showed the first visible emission appeared after the initial current rise. Visible spectroscopy revealed discrete emission lines with strongest components at 426.0 and 656.2 nm. A pressure increase of about 5 $\times$ 10$\sp{-6}$ Torr occured for each breakdown event, with constituents at 12, 28, and 44 atomic mass units. Damage tracks 10 to 50 $\mu$m in diameter were seen with SEM and showed signs of filamentary current flow with melting. Breakdown could be inhibited by illumination with 1064 and 532 nm laser pulses before application of the electric field. A model of silicon surface breakdown is presented which shows heating of conducting channels due to surface band bending or streamer propagation could lead to breakdown on the time scales observed experimentally. Gallium arsenide exhibits a mode termed "lock-on" in which breakdown occurs after illumination. Measurements of the distribution of electric field in a GaAs switch utilizing the Franz-Keldysh effect are reported. Calibration measurements showed the validity of the measurement. Absorption images of a lateral geometry GaAs switch revealed electric field domains up to 50 kV/cm appearing only with laser activation. The number of domains and their field intensity increased with increasing applied field and laser intensity. Lock-on filaments developed normal to the direction of the domains, and tended to relax the electric field.
Subject Area
Electrical engineering
Recommended Citation
Peterkin, Frank Edwin, "Breakdown studies of high-voltage silicon and gallium arsenide photoconductive switches" (1994). ETD collection for University of Nebraska-Lincoln. AAI9519545.
https://digitalcommons.unl.edu/dissertations/AAI9519545