The intersubband transitions in Si delta-doped GaAs structures is theoretically investigated for different applied electric fields. For an uniform distribution the electronic structure has been calculated by solving the Schrodinger and Poisson equations self-consistently. From our calculations, it is found that the subband energies and intersubband optical absorption is quite sensitive to the applied electric field. This gives a new degree of freedom in various device applications based on the intersubband transitions of electrons. (C) 2003 Elsevier Science Ltd. All rights reserved.