Date of Award

Spring 1990

Document Type


Degree Name

Doctor of Philosophy (PhD)


Electrical & Computer Engineering


Electrical Engineering

Committee Director

Karl H. Schoenbach

Committee Member

R. Joshi

Committee Member

V. Lakdawala

Committee Member

D. Cook

Committee Member

G. McRee


This dissertation describes some of the properties of copper-compensated, silicon-doped GaAs (Cu:Si:GaAs) with the purpose of demonstrating the feasibility of the Bulk Optically Controlled Switch (BOSS) concept. The BOSS concept involves the excitation of electrons or holes from selected deep centers in the band gap of a bulk Cu:Si:GaAs photoconductor. The conductivity of the Cu:Si:GaAs crystal can be increased or decreased on command by irradiating the crystal with laser light of different wavelengths in the infrared. Photoconductivities as large as 1 (Ω cm)-1 were measured to persist for microseconds after illumination by a 7 ns laser pulse with wavelength λ= 1064 nm. Strong optical quenching of this photoconductivity over a nanosecond time scale has been observed during illumination with a second laser pulse of wavelength λ > 1500 nm. During the conduction phase, currents as large as 10 kA/cm2 have been measured after the crystal withstood fields as large as 19 kV/cm. Dark conductivities of GaAs crystals grown with a silicon doping density of 5 x 1016 cm-3 have been measured after copper diffusion to range from 1.5 x 10-2 (Ω cm)-1 to as low as 1.4 x 106 (Ω cm)-1. These differences are interpreted to be the result of controlled compensation of the crystal resulting in the conversion of the crystal from strongly n-type (undercompensated) to weakly p-type (overcompensated). The actual level of compensation at thermal equilibrium is shown to have an important effect on the photoconductivity properties of the crystal.