  We report experimental observation of Kondo-Fano resonant tunneling in
Si-doped GaAs/AlAs multiple quantum wells. The spectrum of differential
tunneling conductance at low bias shows a strong temperature dependent
resonance, whose peak is split in the presence of a magnetic field,
characteristic of a Kondo resonance. The data is well explained as a resonant
tunneling of conduction electrons at the Fermi level through the doped silicon
impurity states inside the wells by using an impurity Anderson model. The
Coulomb blockade resonance of the impurity states induces a Fano dip above the
Kondo resonance.
