We have successfully grown ferromagnetic MnGa ultrathin films on GaAs substrates by molecular beam epitaxy. Reflection high energy electron diffraction and cross-sectional transmission electron microscopy show that monocrystalline MnGa films are grown with the c axis of the tetragonal unit cell normal to the (001) GaAs substrates. Both magnetization measurements by vibrating sample magnetometer and extraordinary Hall effect (EHE) measurements indicate perpendicular magnetization, with the remnant magnetization of 225 emu/cm3 and EHE resistivity in the range of 0.5–4 μΩ cm at room temperature. The material possesses properties ideal for certain nonvolatile magnetic memory coupled with underlying III-V circuitry.

A hybrid oscillator operating at 12 GHz and 77 K was designed and characterised. The design incorporated on a single substrate a passive superconductive circuit and a 111-V active device. YBaCuO films (300nm), grown on MgO, had a surface resistance at 77 K of 0.3 m a scaled to 12 GHz. The DC and RF characteristics of the pseudomorphic HEMT showed minor differences before and after hybridation. The characterisation of a preliminary prototype oscillator including a superconducting resonator patterned on a MgO substrate, a gold matching network fabricated on A1203 and a transistor wire bonded gave a phase noise as low as-75 dBc/Hz at 10 KHz.

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