Modulations in alternated tensile/compressive strained GaInAsP multilayer grown by gas source molecular beam epitaxy

Zero-net strained GaInAsP multiple quantum wells grown by gas source molecular beam epitaxy exhibit altered structural and optical properties when tensile barriers are introduced instead of lattice matched ones. Transmission electron microscopy observations have revealed that a modulation of thickness, strain, and probably chemical composition within the layers are responsible for this degradation. The modulation is strongly anisotropic with a period of 50 nm along the [110] direction. Although it is not yet entirely clear, the comparison with relaxed systems and with elastic relaxation models permits a conclusion that this mechanism is induced by a partial relaxation of strain. The amplification of the modulation as well as the opposite behavior between tensile and compressive layers are explained in this manner