We demonstrate heteroepitaxial growth of GaAs/Ge buffer layers for fabricating 1.3-µm range metamorphic InGaAs-based multiple quantum well (MQW) lasers in which the Ge buffer layer is grown using a metal-organic Ge precursor, iso-butyl germane, in a conventional metal-organic vapor phase epitaxy reactor. This enables us to grow Ge and GaAs buffer layers in the same reactor seamlessly. Transmission electron microscopy and X-ray diffraction analyses indicate that dislocations are well confined at the Ge/Si interface. Furthermore, thermal-cycle annealing significantly improves crystalline quality at the GaAs/Ge interface, resulting in higher photoluminescence intensity from the MQWs on the buffer layers.

A 2-step deposition technique was introduced in the heteroepitaxial growth of barium titanate (BaTiO3) thin films. Heteroepitaxial BaTiO3 films were prepared on a SrRuO3/SrTiO3 substrate by radio frequency (RF) magnetron sputtering with three kinds of deposition method: low RF-power deposition, 2-step deposition, and high power deposition. The crystallographic and ferroelectric properties were evaluated for the heteroepitaxial films. When the epitaxial capacitor was prepared by the 2-step deposition technique, the ferroelectric remanent polarization, 2Pr, was maximized. The optimized deposition condition to improve the crystal quality is discussed in terms of damage and diffusion, which could be introduced into the oxide films during the epitaxial growth, and controlled by the RF-power and deposition time, respectively.

To investigate the possibility of their application to both high density dynamic and nonvolatile ferroelectric random access memories, heteroepitaxial BaxSr1-xTiO3 (BSTO) thin films with various Ba content from x=0 to 1. 0 were prepared on conductive SrRuO3 electrode films, and the crystallographic, dielectric and ferroelectric properties were investigated. The compositional phase boundary between paraelectric and ferroelectric phase at room temperature was located at about x = 0. 12 in the heteroepitaxial films, indicating a quite different composition to that of the bulk (x = 0. 70). At this composition of x = 0. 12, the dielectric constant attained the maximum value of 740 for the BSTO film with a thickness of 77 nm. The composition with a lager Ba content (x 0. 32) showed ferroelectricity at room temperature. The maximum value of remanent polarization of 2Pr = 0. 38 C/m2 was obtained at the composition of x = 0. 70 in this study.