WANNIER-STARK LOCALIZATION IN SUPERLATTICES

We present experimental and theoretical evidence for Wannier-Stark (WS ) oscillations in the DC electric current through reverse-biased highl y doped p-i-n GaAs diodes. The intrinsic region in the diode contained seven (GaAs)(5)/(AlAs)(2) multi-quantum wells. Carrying out these tra nsport experiments at low temperatures, we found periodic WS oscillati ons in the second derivative of the Zener current, which is in qualita tive agreement with theoretical predictions based on a realistic multi band and multichannel scattering theory. These findings resolve long-s tanding controversies about the existence of Wannier-Stark levels in t he Zener tunneling current.