Optical absorption of the intersubband transitions in GaAs/Al0.4Ga0.6As multiple quantum wells with superlattice barriers

Abstract

The optical absorption of intersubband transitions in n-type GaAs/Al0.4Ga0.6As multiple quantum wells with superlattice barriers is studied as a function of temperature. The room-temperature spectrum shows a strong intersubband transition at 118.64 meV (10.45 μm) and a shoulder at 137.00 meV (9.05 μm). A broad transition is also observed at 204.6 meV (6.06 μm). The 118.64 meV intersubband transition exhibits a blue shift (∼5.33 meV) as the temperature is decreased from 295 to 4.2 K. The intensity of this transition is increased dramatically while the intensity of the shoulder observed at 137.00 meV is reduced as the temperature is decreased. Theoretical calculations based on a self-consistent k⋅p model which include many-body effects of Hartree, exchange-correlation, depolarization, and vertex effects indicate that the 118.64 meV intersubband absorption is due to the electronic transition between the ground and excited states in the well. On the other hand, the shoulder seems to correspond to a transition between the ground state and the miniband formed in the superlattice barrier.