This article investigates the effects of asymmetric Fabry–Perot (AFP) cavity structures on the switching dynamics of symmetric self-electro-optic effect devices (S-SEEDs) made ofAlxGa1−xAs/GaAs(x⩽0.05)extremely shallow quantum wells (ESQWs). We analyze the switching dynamics of AFP ESQW S-SEEDs (AE-SEEDs) by means of an impulse photocurrent response function and corresponding voltage transients of the two AFPp-i(ESQWs)-ndiodes connected in series. The photocurrent response function is obtained by using an appropriate electron-hole pair generation rate and the Green’s function method. The response function includes the LO phonon scattering from bound to continuum states and the carrier transit in the continuum states. Large internal optical fields and thin intrinsic region thicknesses of AFP SEEDs reduce the required incident switching energy and operating voltage, respectively. Our analyses show that the switching energy of an impedance-matched AE-SEED is about3.0 fJ/&mgr;m2,while that of a conventional antireflection coated ESQW S-SEED (E-SEED) is about4.1 fJ/&mgr;m2.Considering practicalRCtime constants and device sizes, the switching time of an impedance-matched AE-SEED is found to be as low as 10 ps while that of an E-SEED is about 18 ps for the same incident energy of4.1 fJ/&mgr;m2.©1997 American Institute of Physics.