Stress evolution in GaAsN alloy films

Abstract

We have investigated stress evolution in dilute nitride GaAs1−xNxGaAs1−xNx alloy films grown by plasma-assisted molecular-beam epitaxy. For coherently strained films (x<2.5%)(x<2.5%), a comparison of stresses measured via in situ wafer curvature measurements, with those determined from x-ray rocking curves using a linear interpolation of lattice parameter and elastic constants, suggests significant bowing of the elastic properties of GaAsN. The observed stress differences are used to quantify the composition-dependent elastic constant bowing parameters. For films with x>2.5%x>2.5%, in situ wafer curvature measurements reveal a signature for stress relaxation. Atomic force microscopy and transmission electron microscopy measurements indicate that stress relaxation occurs by a combination of elastic relaxation via island formation and plastic relaxation associated with the formation of stacking faults.