The two-dimensional electron gas in &dgr;-doped double quantum wells has been studied by using the Shubnikov–de Haas measurement. It was discovered that the &dgr;-doping layer at the central barrier is able to prevent the electron coupling in the two wells and that the persistent photoconductivity can be reduced due to the thinner barrier. A &dgr;-doped multiple quantum well structure for photodetector application was also proposed. ©1997 American Institute of Physics.