Epitaxial SrTiO3(STO) film on epitaxial (Ti,Al)N/Si(100) was successfully obtained using a Ti-buffer layer. The SrTiO3 film was (100) oriented and grew in parallel epitaxial relationship (cube-on-cube), i.e., (100)SrTiO3//(100)(Ti,Al)N//(100)Si, <110> SrTiO3//<110> (Ti,Al)N//<110> Si. The Ti-buffer layer was grown on (Ti,Al)N by magnetron sputtering, and the thickness of the buffer layer was 2-10 nm. After the STO film was sputtered, the Ti-buffer layer was changed to polycrystalline anatase-TiO2.

A MMIC power amplifier operating with a single-supply (3.0 V) has been developed for 5.8 GHz Japanese Electronic Toll Collection (ETC) System. The present MMIC contains two FETs, matching circuits (input, intermediate and output matching circuits), and two drain bias circuits. High dielectric constant material SrTiO3 (STO) is used for by-pass and input coupling capacitors. Very small die size of 0.77 mm2 has been realized by using the STO capacitors and negative feedback circuit technology. High 1 dB output gain compression point (P1dB) of 13 dBm, high gain of 21.4 dB and low dissipation current of 41.3 mA have been achieved under 3.0 V single-supply condition.

This paper describes design approach and power performance of a single 1. 5 V operation two-stage power amplifier MMIC for 2. 4 GHz wireless local area network applications. The MMIC with 0. 760. 96 mm2 area includes SrTiO3 (STO) capacitors with a high capacitance density of 8. 0 fF/µm2 and double-doped AlGaAs/InGaAs/AlGaAs heterojunction FETs with a shallow threshold voltage of -0. 24 V. Utilizing a series STO capacitor and a shunt inductor as an output matching circuit, the total chip size was reduced by 40% as compared with an MMIC utilizing SiNx capacitors. Under single 1.5 V operation, the developed MMIC delivered an output power of 110 mW (20.4 dBm) and a power-added efficiency (PAE) of 36.7% with an associated gain of 20.0 dB at 2.4 GHz. Even operated at a drain bias voltage of 0.8 V, the MMIC exhibited a high PAE of 31.0%.

Two types of hetero-epitaxial PbZr0. 48Ti0. 52O3 (PZT) capacitors were fabricated by pulsed laser deposition (PLD). One has an Au/PZT/SrRuO3(SRO)/SrTiO3(STO) structure with remanent polarization (Pr) of 32. 1 µC/cm2. The other has an Au/PZT/La-doped STO (La: STO) structure with Pr of 9. 6 to 13. 5 µC/cm2. X-ray diffraction patterns show that only the (00l) planes of the PZT and SRO are parallel to the substrate surface for the PZT/SRO/STO structure, however, a (111) plane of the PZT is observed, in addition to the (00l) planes, for the PZT/La: STO structure. High resolution-transmission electron microscope (HR-TEM) images show that the PZT/SRO interface is clean and coherent. However, spherical shape contrast with radius about 5 nm is observed at the PZT/La: STO interface. Diffusion of La and/or the contaminated surface of the La: STO substrate is thought to cause the differences in the PZT orientations and the interfaces, affecting the electrical characteristics of the capacitors.

We have fabricated bi-epitaxial grain boundary junctions in YBa2Cu3O7δ (YBCO) thin films by using SrTiO3 (STO) seed layers on MgO(100) substrate. YBCO film growing over the STO seed layer has a different in-plane orientation from YBCO film without the seed layer, so artificial grain boundaries were created at the edge of the seed layer. The fabricated junctions have high Tc (up to 80 K), and constant-voltage current steps are observed in response to 12.1 GHz microwave radiation. Moreover, some of the junctions show characteristic current-voltage curves comprising not only an usual Josephson-like characteristic but also a low critical current due to the flux creep. This suggests that the two characteristic parts are likely to be connected in series at the junction region.