lntersubband transitions in pseudomorphic lnGaAs/GaAs/ AIGaAs multiple step quantum wells

Intersubband transitions from the ground state to the first and second excited states in pseudomorphic AlGaAs/lnGaAs/GaAs/ AlGaAs multiple step quantum wells have been observed. The step well structure has a configuration of two A1GaAs barriers confining an InGaAs/GaAs step. Multiple step wells were grown on GaAs substrate with each InGaAs layer compressively strained. During the growth, a uniform growth condition was adopted so that inconvenient long growth interruptions and fast temperature ramps when switching the materials were eliminated. The sample was examined by cross-sectional transmission electron microscopy, an x-ray rocking curve technique, and the results show good crystal quality using this simple growth method. Theoretical calculations were performed to fit the intersubband absorption spectrum. The calculated energies are in good agreement with the observed peak positions for both the 1 ___, 2 and 1 ___, 3 transitions.