High temperature device characterstics of GaAs MESFETs fabricated with an AlAs buffer layer

High temperature electronics (HTE) are required for automotive, aircraft, space and other applications exposed to thermal extremes. Many HTE efforts have focused on very wide bandgap semiconductors (>2.5eV) such as Sic, GaN and diamond [l], [2]. However, GaAs (a more mature technology) also shows promise for high temperature applications (<400"C) because it provides a reasonably wide bandgap (1.42eV) with high mobility. Unfortunately, when GaAs MESFETs are evaluated at temperatures greater than 250°C large subthreshold drain currents degrade device performance by reducing switching ratios and increasing output conductances [3]. A potential solution to the problem of large subthreshold currents is explored in this investigation. By incorporating an undoped AMs buffer layer beneath the active channel of a GaAs MESFET, a marked reduction in subthreshold current is observed at temperatures as high as 350°C.