Using infrared (IR) photomodulation spectroscopy in lightly doped GaAs/AlGaAs multiple quantum wells (MQW), we study the changes in the e1-e2 intersubband absorption due to the interband excitations. For the barrier doped MQWs, we find that an impurity level which is ∼ 60 meV below the barrier band-gap, strongly affects both the shape and intensity of the intersubband transitions. No such effects are observed in the well-doped MQWs.
Bibliographical noteFunding Information:
The work at the Tcchnion was supported by the US-Israel Binational Science Foundation (BSF), Jerusalem, Israel and by the Technion Fund for the Promotion of Research. The work at UCSB was supported by the National Science Foundation Science and Technology Center, QUEST.