Photocurrent spectroscopy in GaAs/AlGaAs multiple quantum wells under a high electric field perpendicular to the heterointerface

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Abstract
Photocurrent (PC) spectroscopy under high electric fields perpendicular to the heterointerface has been utilized to characterize subband structures in GaAs/AlGaAs multiple quantum wells (MQW’s). The PC spectra from MQW’s under high electric fields show clear exciton peaks corresponding to forbidden transitions between electron and hole subbands. From PC spectra, we have precisely determined the splitting energies of the two lowest electron and four highest hole subbands in 55-, 82-, and 105-Å-thick wells. The experimental results indicate that the conduction-band offset is 60±3% of the band-gap discontinuity. Our data are also in excellent agreement with finite square well calculations using a heavy-hole effective mass of 0.34 and a light-hole effective mass of 0.12.