Impact of GaAs buffer thickness on electronic quality of GaAs grown on graded Ge/GeSi/Si substrates

Minority carrier lifetimes and interface recombination velocities for GaAs grown on a Si wafer using compositionally graded GeSi buffers have been inv estigated as a function of GaAs buffer thickness using monolayer-scale cont rol of the GaAs/Ge interface nucleation during molecular beam epitaxy. The GaAs layers are free of antiphase domain disorder, with threading dislocati on densities measured by etch pit density of 5 x 10(5)-2 x 10(6) cm(-2). An alysis indicates no degradation in either minority carrier lifetime or inte rface recombination velocity down to a GaAs buffer thickness of 0.1 mu m. I n fact, record high minority carrier lifetimes exceeding 10 ns have been ob tained for GaAs on Si with a 0.1 mu m GaAs buffer. Secondary ion mass spect roscopy reveals that cross diffusion of Ga, As, and Ge at the GaAs/Ge inter face formed on the graded GeSi buffers are below detection limits in the in terface region, indicating that polarity control of the GaAs/Ge interface f ormed on GeSi/Si substrates can be achieved. (C) 2000 American Institute of Physics. [S0003-6951(00)03214-9].