New type of Fano resonant tunneling via Anderson impurities in superlattice

¹ Department of Physics and HKU-CAS Joint Laboratory on New Materials The University of Hong Kong - Pokfulam Road, Hong Kong, PRC
² National Laboratory of Solid State Microstructures and Department of Physics Nanjing University - Nanjing 210093, PRC
³ State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences - Beijing 100083, PRC

Corresponding author: sjxu@hkucc.hku.hk

Received: 28 February 2006
Accepted: 5 April 2006

Abstract

The spectrum of differential tunneling conductance in Si-doped GaAs/AlAs superlattice is measured at low electric fields. The conductance spectra feature a zero-bias peak and a low-bias dip at low temperatures. By taking into account the quantum interference between tunneling paths via superlattice miniband and via Coulomb blockade levels of impurities, we theoretically show that such a peak-dip structure is attributed to a Fano resonance where the peak always appears at the zero bias and the line shape is essentially described by a new function with the asymmetry parameter . As the temperature increases, the peak-dip structure fades out due to thermal fluctuations. Good agreement between experiment and theory enables us to distinguish the zero-bias resonance from the usual Kondo resonance.