We theoretically analyze effects of the piezoelectric field and its screening on the electronic and optical properties including optical matrix element and spontaneous emission for InxGa1-xAs/GaAs superlattices (SLs). For the investigation we take  In0.15Ga0.85As/GaAs SL with three types of structures according to well/barrier widths of 40 Å/40 Å, 100 Å/100 Å, and 160 Å/160 Å. The carrier densities are assumed to be equivalent to 5×1016, 1×1017, 5×1017, 1×1018, and 5×1018 cm-3 over 40 Å width in the wells. In the numerical computations, we use the computation model presented recently by [B. W. Kim, J. H. Yoo, and S. H. Kim, ETRI Journal 21, 65 (1999)]. The model self-consistently solves 8×8 (conduction, heavy, light, and spin split-off valence bands) effective-mass Schrödinger equation and the Hartree and exchange-correlation potential equations through the variational procedure. The results show that piezoelectric field causes significant changes in the electronic and optical properties; however, the screening of piezoelectric field by the carriers in the wells seems not very effective for device application. © 2001 American Institute of Physics.