MODELING OF A LOW-INTENSITY ELECTROOPTICAL SEMICONDUCTOR SWITCHING DEVICE DUE TO INTRINSIC PHOTOCONDUCTIVITY

An electro-optical device consisting of a stack of undoped alternating layers of narrow- and wide-gap materials (e.g., GaAs/AlGaAs) together with a series resistor under constant voltage bias is analyzed theore tically. The GaAs heterolayers with a width in the order of a carrier mean free-path are a photo-active region of this vertical device. The device operates only in the presence of a low-intensity light beam due to the intrinsic photoconductivity of the active region. The Franz-Ke ldysh effect, the strong accumulation of the photocarriers in the phot oactive layers due to the charge separation in the presence of the sta tic electric field, and the ballistic component of the total current a re responsible for the unusually large electro-optical nonlinearity of the device. Kirchhoff's law for the electrical circuit of the device provides a sensitive feedback between the voltage drop over the layer and the photocurrent. In a Fabry-Perot cavity a room temperature elect ro-optical bistabitity is obtained at light intensities less than 10 m W/cm2 with a switching time of about 100 ns.