Strain splitting of the X-conduction-band valleys and quenching of spin-valley interaction in indirect GaAs/AlxGa1-xAs:Si heterostructures

We report electron-paramagnetic-resonance results for the shallow effective-mass 1s(T2) state of the Si donor associated with the X valleys in indirect-band-gap (x0.4) AlxGa1-xAs layers grown on GaAs. The data confirm definitely that the heteroepitaxial strain splits the three X valleys such that the Xz valley lies above the Xx and Xy valleys. An independent-valley model perfectly accounts for the properties of the donor resonance over the full indirect-band-gap range of the alloy without inclusion of the spin-valley interaction. This effect is attributed to small local, random in-plane strains which quench the first-order spin-valley splitting. © 1990 The American Physical Society.