Photocurrent spectroscopy of low-electric-field anticrossings in semiconductor superlattices

We have investigated the anticrossings of Wannier-Stark levels at low elect ric fields in a superlattice with wide quantum wells by photocurrent spectr oscopy. The measurements were performed at low temperatures in electric and magnetic fields parallel to the growth direction. The diamagnetic shift of the excitonic Wannier-Stark levels was measured for constant electric fiel ds smaller and higher than the resonance electric field. By comparing the d iamagnetic shift of the various transitions, the character of the states in volved in the anticrossing was determined and the interchange of the states during the low-field anticrossing could be verified. Furthermore, the inte rwell-to-intrawell ratio of the diamagnetic shift is compared to theoretica l calculations of the exciton radius. [S0163-1829(99)16031-4].