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

An optical modulator based on electric field induced charge transfer in a double quantum well structure is introduced. The modulator is configured as n-i-n diode for waveguide applications at a wavelength of almost-equal-to 1 mum. Dark currents caused by thermionic emission are suppressed by introducing specially designed InGaAs/AlGaAs hetero barriers. Room temperature operation with negligible dark current up to internal electric fields of 1.7 x 10(5) V/cm is demonstrated. Electric field tunable absorption is obtained by both band filling and Stark effect in a GaAs/InGaAs double quantum well unit which has been repeated five times in the i-region of the n-i-n structure. Absorption spectroscopy is performed in waveguide geometry and applications as optical modulators are demonstrated.