We performed low-temperature (77 K) photomodulated transmission in two different Inx Ga1-xAs/GaAs superlattices with fixed built-in fields. Sample parameters are such that in one of them electrons are in the Stark-Wannier field regime while in the other they are in the Franz-Keldysh regime. In both samples, however, light holes are seen to be in the Franz-Keldysh regime. From this we infer that the light-hole valence bands are essentially lined up on both sides of the InxGa1-xAs/GaAs heterojunction. © 1994 The American Physical Society.49322462249