Highspeed 1.3-μm GalnAs Detectors Fabricated on GaAs Substrates

High-speed interdigitated metal-semiconductor-metal (IMSM) detectors have been fabricated on non-lattice-matched, semiinsulating, GaAs substrates using two GalnAs layers of differing indium concentrations to accommodate most of the lattice mismatch via interface misfit dislocations. Bandwidths as high as 3 GHz were measured with none of the detrimental low-frequency gain usually observed in this type of device. This is attributed to the inhibition of the surface trapping of photoinduced carriers by means of a graded pseudomorphic layer at the surface. © 1988 IEEE.