GaAs‐AlGaAs quantum wires with various widths have been fabricated using electron beam lithography and Ar ion etching. Conductance was measured as a function of the etched depth and the wire width. The results indicate that defects diffuse at room temperature. Shubnikov–de Haas oscillations in GaAs‐AlGaAs film and wires with different widths have been measured to investigate the effect of the surface damage on the electron transport characteristics. The analysis of the results shows that both electron density and scattering time decrease with decreasing the width of the channel. These are indicative of the side wall scattering and the damages induced during the sample preparation process.