Abstract
Room temperature Phototransmitance and Electrotransmitance have been applied to high quality 50 A and 250 A InxGa1-xAs/In0.52Al0.48As single quantum wells grown by MBE for two nominal In compositions x=0.53 and x=0.6. Several interband excitonic transitions between confined carrier states have been clearly resolved. An observed red shift of the transition energies when an DC electric field is applied perpendicular to the layers, may be attributed to the Quantum Confined Stark Effect.