Conduction-band spin splitting of type-I ${\mathrm{Ga}}_{\mathit{x}}$${\mathrm{In}}_{1\mathrm{-}\mathit{x}}$As/InP quantum wells

The spin-splitting factor ${\mathit{g}}^{\mathrm{*}}$ of the electrons at the very bottom of the conduction band in strained ${\mathrm{Ga}}_{\mathit{x}}$${\mathrm{In}}_{1\mathrm{-}\mathit{x}}$As/InP type-I quantum wells is reported. Experimental proof of quantum confinement-dependent anisotropy of ${\mathit{g}}^{\mathrm{*}}$ is given. Changing the alloy composition at fixed quantization, equivalent to introducing compressive and tensile strain, changes ${\mathit{g}}^{\mathrm{*}}$. The values of ${\mathit{g}}^{\mathrm{*}}$ perpendicular to the quantum-well plane can be explained in a model calculation. Apparently however, no quantitative theory on which to base the calculation of the anisotropic spin splitting is at present available.