BREAKDOWN VOLTAGE IMPROVEMENT IN STRAINED INGAALAS/GAAS FETS

GaAs MESFET's with a surface layer of pseudomorphic InGaAlAs have been fabricated. The compressive strain and wide bandgap in the InGaAlAs layer reduce the impact ionization rate in this layer and improve the breakdown voltage of the device. A 1-mu-m x 75-mu-m gate device with the pseudomorphic surface layer showed an improvement in gate-to-drain breakdown of over 55% and an improvement in channel breakdown of 50% as compared to a similar device without the pseudomorphic layer. Both devices had a peak transconductance or about 190 mS / mm and a saturation current of about 265 mA / mm.