We have observed Wannier–Stark localization in extremely shallow superlattices (SL) at 77 K, which results in a quasi‐blue shift of the absorption edge at very small electric fields. The formation of a Stark ladder is also clearly shown. The blue shift results in a change in absorption coefficient from 1.7 &mgr;m−1(at 0.2 V/&mgr;m) to 0.98 &mgr;m−1(at 0.6 V/&mgr;m) for a GaAs/Al0.07Ga0.93As SL; for a GaAs/Al0.02Ga0.98As SL we obtain a change from 2.1 &mgr;m−1(at 1.1 V/&mgr;m) to 0.9 &mgr;m−1(at 1.5 V/&mgr;m).