Dislocation reduction in InP layers grown on sawtooth-patterned GaAs substrates

We report on the crystalline improvement of InP layers grown on GaAs substrates by using sawtooth-patterned substrates. The period of sawtooth pattern was 1.2 μm and the layers were grown by low-pressure metalorganic chemical vapor deposition. Cross-sectional transmission electron microscope observation is applied to examine the effectiveness of the sawtooth-shaped hetero-interface for the reduction of threading dislocations in InP layers which accommodate lattice mismatch. A remarkable decrease in the full width at half-maximum values of the X-ray diffraction peaks was obtained, signifying a dramatic crystalline improvement due to the reduction of dislocations by the sawtooth-shaped interface. The unevenness of the layer surface which originates from the sawtooth shape of the substrate can be readily smoothed by thermal cycle annealing, which is accompanied by additional crystalline improvement. Moreover, an attempt to put a thin strained interlayer in the epitaxial layer as a defect filtering tool is also presented.