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 grow n on (001) GaAs slightly misoriented (2 degrees-6 degrees) towards (11 1)A exhibits a blue shift when compared to quantum wells grown on perf ectly oriented substrates. It is shown that this observation is linked to a blue shift of intrinsic ground state excitonic transition energi es. This effect is studied as a function of substrate misorientation a ngle, well width and indium surface segregation level. In order to und erstand its origin, various hypotheses were examined: regular shrinkag e of well width due to terrace edges, additionnal stress of the well m aterial at the step edges, and orientation dependent In segregation. I t appears that the first two combined effects provide the best descrip tion of the experimental tendency.