The luminescence properties of a new superlattice structure, called a n-i-p-i heterostructure, are described. The samples consist of GaAs quantum wells placed between alternately doped Al1-xGaxAs layers. The luminescence transitions between the quantized GaAs subbands are greatly influenced by the excitation-intensity-dependent electrostatic potential. The lowest subband luminescence transition agrees well with predictions for the ideal structure. In addition, distinct luminescence transitions from higher subbands are observed.