CHARGE-TRANSFER AND ELECTROABSORPTION IN AN ELECTRIC-FIELD TUNABLE DOUBLE-QUANTUM-WELL STRUCTURE

An optical modulator based on electric field induced charge transfer i n a double quantum well structure is introduced. The modulator is conf igured as n-i-n diode for waveguide applications at a wavelength of al most-equal-to 1 mum. Dark currents caused by thermionic emission are s uppressed by introducing specially designed InGaAs/AlGaAs hetero barri ers. Room temperature operation with negligible dark current up to int ernal electric fields of 1.7 x 10(5) V/cm is demonstrated. Electric fi eld tunable absorption is obtained by both band filling and Stark effe ct in a GaAs/InGaAs double quantum well unit which has been repeated f ive times in the i-region of the n-i-n structure. Absorption spectrosc opy is performed in waveguide geometry and applications as optical mod ulators are demonstrated.