Compositional variations in InGaAsP films grown on patterned substrates

A comparison of the growth behaviour of lattice-matched In0.53 Ga0.47 As and In0.74 Ga0.26 As0.59P0.41 films on InP substrates, patterned as diffraction gratings, has been carried out using analytical electron microscopy. Ga enrichment above the ridge of the grating was found in both the ternary and quaternary alloys. In the final stages of growth of a 100 nm thick ternary alloy film, the Ga enrichment was confined to a narrow strip, 3 nm in width, lying directly above the ridge. The partitioning of alloying elements during growth led to regions of the film that were locally under tension or compression, as seen by diffraction contrast. The films showed strikingly different planarization behaviour that appears to correlate with the In content.