Epitaxial films of the full Heusler alloy Co2MnAl were grown on GaAs substrates by molecular-beam epitaxy. The close lattice matching and similar structure to GaAs make this material a good candidate for a spin injector. Magnetization measurements reveal complex ferromagnetic transitions near the Curie point at TC≃800 K. At room temperature, magnetotransport studies show metallic behavior and a giant Hall effect driven by the extraordinary Hall effect.

High-temperature threshold characteristics of a symmetrically graded δ-doped InAlAs∕InxGa1−xAs∕GaAs (x=0.5→0.65→0.5) metamorphic high electron mobility transistor (MHEMT) have been investigated. The thermal threshold coefficients, defined as ∂Vth∕∂T, are superiorly low at 0.9mV∕K from 300to420K and at −0.75mV∕K from 420to500K. An interesting polarity change of the thermal threshold coefficient was observed around 420K due to the variation of thermal modulation effects. The present MHEMT device, with stabilized thermal threshold variations and superior high-temperature linearity characteristics, is promising for high-temperature circuit applications.