Using electro- and photoreflectance with a spatial resolution of≈10 &mgr;mwe have evaluated the energy of the fundamental conduction to heavy-hole (1C–1HH) quantum transition of a fabricated 0.98 &mgr;m InGaAs/GaAs/InGaPp-i-nquantum well laser structure as a function of bias and position on the laser stripe. From a comparison of the measured forward/reverse bias dependence of the1C–1HH energy with a theoretical calculation of the quantum confined Stark effect, we have been able to evaluate the built-in electric field and width of the insulating region. ©1997 American Institute of Physics.