Growth of GaAs and InGaAs on patterned silicon substrates for photodiode applications

GaAs and In_xGa_1-xAs have been grown on both planar silicon wafers and on silicon wafers etched to leave restricted island regions, proud of the surrounding substrate material. The reverse leakage currents of In_xGa_1-xAs p-i-n photodiodes were found to be lower for growth on islands, with devices fabricated on the smallest islands showing leakage current densities of 1.3×10 ^-4 A/cm² at -5 V bias. This effect has been attributed to a lower density of threading dislocations for growth on small islands