Effects of uniaxial stress on the optical properties of GaAs and GaAs/Ga1-xAl1-x As single quantum wells grown on Si(001) substrates

The effects of a large external uniaxial stress (sigma) along [100] on the optical features associated with biaxially strained bulk GaAs and two GaAs/Ga1-xAlxAs single quantum wells (SQWs), with widths of 52 and 200 angstrom, grown on Si(001) have been studied using photoreflectance at 77 and 300 K. Measurements were made with incident light polarized parallel and perpendicular to sigma. This stress configuration makes it possible to externally alter the light-hole (LH) and heavy-hole (HH) splitting in both the bulk material and the SQWs. In the SQW of width 200 angstrom, the ground-state valence band was continually tuned from HLs to HHs. In the bulk material, a stress-induced anticrossing of the LH and HH features of the fundamental gap was observed with an interesting polarization effect.