Photoreflectance and photoluminescence study of step-like GaInNAs/GaInNAs/GaAs quantum wells

GaInNAs-based quantum well (QW) structures tailored at 1.55 (mu)m are investigated by photoreflectance (PR) and photoluminescence (PL) spectroscopies. The PL intensity and the energy level structure are compared for two types of QWs: GaInNAs/GaAs single QW (SQW) and step-like barrier GaInNAs/GaInNAs/GaAs QW (SLBQW) structures. It is observed that the reduction of N atom concentration in the active QW region from 5.3% (SQW) to 2-2.5% (SLBQWs) leads to the enhancement of PL intensity by a factor of five. Moreover, the introduction of the SLB changes the energy level structure for this system. On the basis of PR measurements, the bandgap energy of the SLB and energies of the transitions in the active QW region were determined. For the structures presented, the SLBs lead to one confined state for electrons and three confined states for heavy holes in the GaInNAs/GaInNAs QW. Transitions related to the three heavy hole sub-bands and the one electron sub-band have been observed in PR spectra.