Twist-bonded compliant substrates for III–V semiconductors heteroepitaxy

Compliant structures have been elaborated so that a thin GaAs layer (thickness about 10 nm) was bonded on top of a GaAs substrate with a large twist angle (about 45°). The mechanical behaviour of such a compliant substructure was investigated by nanoindentation and the results were compared to those obtained on standard bulk substrates. A so-called free-standing behaviour was observed under low load (<0.25 mN). Above an enhancement of the plastic flow was determined. The morphology of relaxed InGaAs heteroepitaxial layer grown in the same conditions on standard and compliant substrates was then compared. We observed a strong decrease of the threading dislocations density in the alloy grown on the compliant substrates that correlates very well with the mechanical behaviour measured on compliant substrates.