In situ measurements of dislocations at growth temperature have been made on the heteroepitaxial systems of GaAs/Si and GaP/Si. It was found that the etch pit densities of heteroepitaxial layers were as low as those of bulk wafers at the growth temperature and increase to 107 cm−2 when the layers cool down to room temperature. This means that the thermal stress determines the quality of heteroepitaxial layers.
The InP on Si system, in which the thermal expansion coefficient difference is smaller than other heteroepitaxial systems, has been studied. High quality InP has been obtained using a GaAs buffer layer, strained-layer superlattice insertion, and thermal cycle annealing and regrowth. Full width at half maximum of X-ray rocking curve was 110" at 13 µ thickness.
An InGaAsP laser diode emitting at 1.55 µm was successfully made on Si. The threshold current was 46 mA at room temperature for a ridge waveguide laser with a 4 µm width and a 200,µm cavity length.