Improved contacts to semi-insulating GaAs photoconductive switches using a graded layer of InGaAs

High performance photoconductive switches are demonstrated using a molecular beam epitaxy grown graded layer of InxGa1-xAs to make an ohmic contact to semi-insultating GaAs. It is found that the graded layer results in a peak signal amplitude that is more than a factor of 2 larger than what is obtained using conventional alloyed AuGeNi contacts.