Molecular beam epitaxial growth and properties of GaAs pseudomorphic high electron mobility transistors on silicon composite substrates

摘要

GaAs pseudomorphic high electron mobility transistor (PHEMT) structures were grown by molecular beam epitaxy on germanium substrates and composite silicon template wafers incorporating silicon and germanium transferred layers. Windows were etched down to the buried germanium layer and subsequent blanket material growth resulted in single crystal growth in the windows and polycrystalline growth on the top SiO_2 surface. Wire growth was eliminated at the window edges and on the top SiO_2 surface. Secondary ion mass spectrometry measurements and transmission electron micrographs of GaAs grown on germanium indicated an abrupt GaAs-Ge interface with little penetration of antiphase boundaries or other defects into the GaAs layer. For PHEMT material grown on silicon template wafers, a surface roughness of 8 A was measured by atomic force microscopy. The room temperature photoluminescence intensity of the InGaAs channel in the PHEMT structure was equivalent to that grown on GaAs substrates. Measured PHEMT mobilities and sheet densities were comparable to those obtained on GaAs substrates. Transistors were fabricated with 0.25 μm gates. The maximum dc current density, 520 mA/mm, and transconductance, 360 mS/mm, were very similar to devices fabricated on GaAs substrates.