An atomically-controlled GaSb layer was fabricated on GaAs(0 0 1) substrates by using the surface exchange reaction between arsenic and antimony atoms. The exchange reaction process was controlled by molecular-beam irradiation of Sb-4 and was monitored by using reflection high-energy electron-beam diffraction (RHEED). One-cycle oscillation of RHEED specular-beam intensity during the Sb4 irradiation was explained by the change of surface structure from GaAs to GaSb. From transmission electron microscopy and photoluminescence (PL) measurements, it was found that fabricated GaAs/GaSb quantum well (QW) structures have an abrupt heterointerface and high crystal quality. In scanning tunneling microscopy measurements, tunneling spectra obtained from the GaSb-terminated GaAs sample revealed suppression of density of surface states. (C) 2004 Elsevier B.V. All rights reserved.