High-speed GaAs metal gate semiconductor field effect transistor structure grown on a composite $Ge∕GexSi1−x∕Si$ substrate

In this study we used a low-pressure metal organic vapor phase epitaxy method to investigate the growth of GaAs metal gate semiconductor field effect transistor (MESFET) structures on a Si substrate. The buffer layer between the Si substrate and the grown GaAs epitaxial layers was a composite $Ge∕Si0.05Ge0.95∕Si0.1Ge0.9$ metamorphic layer. We used transmission electron microscopy to observe the microstructures formed in the grown $GaAs∕Ge∕SixGe1−x∕Si$ material and atomic force microscopy to analyze the surface morphology and the formation of antiphase domains in the GaAs epitaxial layers. The measured Hall electron mobility in the channel layer of a MESFET structure grown on a 6° misoriented Si substrate was $2015cm2V−1s−1$ with a carrier concentration of $5.0×1017cm−3$⁠. The MESFET device fabricated on this sample exhibited good current-voltage characteristics.