Yoshiki Ueno

Solid-Phase Reactions in Al Alloy/TiN/Ti/Si Systems Observed by In Situ Cross-Sectional TEM

The mechanism of solid-phase reactions for multilayers of Al-1%Si-0.5%Cu/TiN/Ti/n+-Si substrates has been investigated by means of in situ and high-resolution/analytical cross-sectional transmission electron microscopy (X-TEM). We have succeeded for the first time in real-time observation of the instant of barrier breakdown of the TiN layer. An intermediate Al-Ti-Si(-N) layer ( ~4 nm thickness) composed mainly of microcrystallites was formed at the Al alloy/TiN interface at ~450° C, and the microcrystalline phase grew along the TiN grain boundaries. At over ~500° C, the Al diffused downward very rapidly through the TiN layer, forming an Al region under the TiN layer. It is concluded that the rapid redistribution of the Al may be caused by movement along the TiN grain boundaries in the microcrystalline state.

Critical layer thickness of In0.80Ga0.20As/In0.52Al0.48As heterostructures

Abstract The critical layer thickness of n-In 0.52 Al 0.48 As/strained-In 0.8 Ga 0.2 As/In 0.52 Al 0.48 As grown on InP substrates was investigated by measuring the photoluminescence spectra. These pseudomorphic heterostructures grown by molecular beam epitaxy attained the highest mobility, 16,200 cm 2 /V·s, at room temperature. The photoluminescence emission intensity decreased in the thickness range of 20 to 25 nm for the In 0.8 Ga 0.2 As layer. These results indicate that the critical layer thickness of this structure follows the energy balance model rather than the mechanical equilibrium model. In addition, this critical value is in good agreement with the results based on the electron mobility behavior.

High Temperature Superconducting Filters for Receiver Front-end of Mobile Telecommunication Base Station

The performance of multi-pole microstrip filters with low insertion loss and sharp-skirt using YBa2Cu3O7-δ high temperature superconducting thin films is presented. The HTS films were deposited on both sides of substrates by a DC sputtering method. The surface resistance of the films was about 0.35mΩ (at 70k and l0GHz). A 9-pole bandpass filter was designed at 2.6GHz center frequency with bandwidth 34MHz. The filter was fabricated using 40mm X 25mm HTS films on a 0.5-mm thick MgO substrate. The insertion loss at 70 K was about 0.ldB with 0.ldB ripple and the minimum return loss was about 20 dB across the passband of the filter. In addition, a 15-pole bandpass filter whose center frequency and bandwidth were 1.53GHz and 60MHz respectively was fabricated using 50-mm diameter HTS film on 0.5-mm thick LaAlO3 substrate. The insertion loss at 70K was less than O.ldB and the rejection level was more than 70dB at the rejection band.

The Performance of the Microstrip Line Resonator and the Bandpass Filter Using YBa 2 Cu 3 O 7-δ Films with a CeO 2 Cap Layer

We investigated the influence that the surface degradation of the YBa2Cu3O7-δ. (YBCO) film during device fabrication exerts on the performances of microstrip line resonators and bandpass filters. The surface of the YBCO films were covered with a CeO2 cap layer to suppress the surface degradation. The microstrip line resonators with a CeO2 cap layer showed the unloaded Q factor (Qu) of 83,400 at 2.6GHz and 70K, while the Qu of the microstrip line resonators without a CeO2 cap layer were 25% lower. The bandpass filters with capacitive interconnections showed almost same frequency response as the one with ohmic interconnections.

Critical Layer Thickness of n-In0.52Al0.48As/In0.8Ga0.2As/In0.52Al0.48As Pseudomorphic Heterostructures Studied by Photoluminescence

Photoluminescence (PL) analysis on n-In0.52Al0.48As/In0.8Ga0.2As/In0.52Al0.48As/InP pseudomorphic heterostructures grown by molecular beam epitaxy has been carried out to investigate the critical layer thickness. Crystal quality degradation is followed by the relaxation of the lattice-mismatched layer. The critical layer thickness for this material system that is measured by PL is found to agree with the value from the energy balance model.