Date of Award

Spring 1995

Document Type


Degree Name

Doctor of Philosophy (PhD)


Electrical & Computer Engineering

Committee Director

Karl H. Schoenbach

Committee Member

Linda Vahala

Committee Member

Ravindra Joshi

Committee Member

Gary E. Copeland


The processes of persistent photoconductivity followed by photo-quenching are demonstrated in copper-compensated, silicon-doped, semi-insulating gallium arsenide. These processes allow a switch to be developed that can be closed by the application of one laser pulse (λ = 1.06 μm) and opened by the application of a second laser pulse with a wavelength equal to twice that of the first laser (λ= 2.13 μm). Switch closure is primarily achieved by elevating electrons from a deep copper center which has been diffused into the material. The opening phase is a two-step process which relies initially on the absorption of the 2-μm laser causing electrons to be elevated from the valence band back into the copper center, and finally on the recombination of electrons in the conduction band with holes in the valence band. The second step requires a sufficient concentration of recombination centers in the material for opening to occur in the subnanosecond regime. Both an experimental and a theoretical investigation of the generation of recombination centers in copper-doped gallium arsenide material, for the purpose of enabling the switch to close as well as open in the subnanosecond regime, is presented. These recombination centers were generated in the bulk GaAs material by fast-neutron irradiation (-1-MeV). An enhanced recombination center density also allows the copper-compensated GaAs switches to open against average electric fields of up to 36 kV/cm corresponding to a switch voltage of 18 kV. Finally, a new high-power radio-frequency (RF) source topology is introduced which uses two copper-doped gallium arsenide switches to synthesize frequency-agile RF waveforms. These waveforms may have considerable advantages when used in high-power-microwave applications.