WANNIER-STARK LOCALIZATION IN SUPERLATTICES

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