Variation of strain in single and multilayer (InxGa1−xAs) structures grown on Si(100), and Si(111), by molecular beam epitaxy

The difference in thermal expansion coefficients between GaAs and Si is known to induce a biaxial tensile strain, below room temperature, for GaAs epilayers grown on Si(100). We have performed photoluminescence (PL) measurements for GaAs layers grown on both Si(111) and misorientated Si(100) substrates by molecular beam epitaxy. These measurements indicate that the thermally-induced strain is greater for the (111) growth direction. Strained InxGa1−xAs-GaAs multiple quantum well structures grown on Si(100), (MQW/Si), exhibit systematic decreases in low temperature PL transition energies when compared with similar structures grown on GaAs(100), (MQW/GaAs). The MQW structures incorporating greater strain (18.7% In content) show decreases in PL transition energies of 3–9 meV between MQW/Si and MQW/GaAs, while MQW structures containing less-strained layers (11% In content) exhibit 12–13 meV shifts to lower transition energies. It seems, therefore, that the effect of thermal strain becomes more pronounced at lower levels of coherency strain