High Minority-Carrier Lifetimes in GaAs Grown on Low-Defect-Density Ge/GeSi/Si Substrates

A high bulk minority-carrier lifetime in GaAs grown on Si-based substrates is demonstrated. This was achieved by utilizing a step-graded Ge/GeSi buffer (threading dislocation density 2×10⁶ cm^-2) grown on an offcut (001) Si wafer, coupled with monolayer-scale control of the GaAs nucleation to suppress antiphase domains. Bulk minority-carrier lifetimes (τ_p) were measured using room-temperature time-resolved photoluminescence applied to a series of Al_0.3Ga_0.7As/GaAs/Al_0.3Ga_0.7As double-heterojunction structures doped n=1.1×10¹⁷ cm^-3 with GaAs thicknesses of 0.5, 1.0, and 1.5 μm. A lifetime τ_p=7.7 ns was determined for GaAs grown on Si. The extracted interface recombination velocity of 3.9×10³ cm/s is comparable to recombination velocities found for Al_0.3Ga_0.7As/GaAs interfaces grown on both GaAs and Ge wafers, indicating that the crosshatch surface morphology characteristic of strain-relaxed Ge/GeSi surfaces does not impede the formation of high-electronic-quality interfaces. These results hold great promise for future integration of III-V minority-carrier devices with Si wafer technologies.