Optical studies of strain effects in quantum wells grown on (311) and (100) GaAs substrates

Abstract

Pseudomorphic InGaAs/GaAs quantum wells (QW's) grown on vicinal substrates show a blueshift of the photoluminescence (PL) emissions with respect to (100) (nominal) ones. This effect has been discussed in the literature and it is associated with an inhomogeneous distribution of stresses in narrow quantum wells. In order to study the shift of the PL emissions at large substrate misorientation angles, we have made PL measurements on three InGaAs/GaAs QW's $(30 \AA{}$ wide), grown on $(311)A,$ $(311)B,$ and (100) substrates. We have done theoretical calculations considering the effect of strain on the conduction and valence bands of the QW's, where a single fitting parameter accounts for the inhomogeneous distribution of strain. Our model agrees with previously obtained results and reproduces the experimental PL blueshifts observed for the studied samples, showing that in relatively wider quantum wells the inhomogeneous distribution of strain and indium segregation play a less important role than in narrow ones. In (100) and $(311)A$ GaAs/AlGaAs samples subjected to an external hydrostatic pressure, our model shows, for both samples, that the blueshift of the QW PL emissions increases with pressure, in good agreement with experimental results, emphasizing the strong relation between strain and blueshift regardless of the growth direction.