Composition fluctuations in GaInNAs multi-quantum wells

GaInNAs/GaAs(001) multi-quantum wells grown by MBE at temperatures in the range 360-460°C have been studied by transmission electron microscopy and photoluminescence. The authors have observed the existence of periodic contrasts with 220BF reflection, which appear more pronounced when increasing the growth temperature. These strain contrasts have been associated to composition fluctuations in the wells and, therefore, it is suggested that an enhancement of the phase separation in the GaInNAs quantum wells occurs when varying the growth temperature from 360°C to 460°C. The photoluminescence results show a broadening of the emission peak over a similar growth temperature range. Thus, the degradation of the optical properties in the GaInNAs structures is suggested to be linked to the composition fluctuations.