Origin of the Blue Shift Observed in Highly Strained (Ga, In)As Quantum Wells Grown on GaAs(001) Vicinal Surfaces

The photoluminescence energy of strained (Ga, In)As quantum wells grown on (001) GaAs slightly misoriented (2°-6°) towards (111)A exhibits a blue shift when compared to quantum wells grown on perfectly oriented substrates. It is shown that this observation is linked to a blue shift of intrinsic ground state excitonic transition energies. This effect is studied as a function of substrate misorientation angle, well width and indium surface segregation level. In order to understand its origin, various hypotheses were examined: regular shrinkage of well width due to terrace edges, additionnal stress of the well material at the step edges, and orientation dependent In segregation. It appears that the first two combined effects provide the best description of the experimental tendency.