Tin-doped indium oxide (ITO) thin films were prepared on a polyethylene terephthalate (PET) foil by bias sputtering. In the absence of a substrate bias, films having a high resistivity of 210-2 Ωcm were formed. On the other hand, by the application of an rf substrate bias, films having a low resistivity of 2.610-4 Ωcm were formed. The energy of ions that bombarded the substrate during bias sputtering was estimated by a simulation of the ion acceleration. The optimum ion-energy required for the reduction of resistivity was found to be approximately 50 eV.

This paper describes new millimeter-wave ICs based on flip-chip bonding using micro bumps on a low cost silicon substrate, named millimeter-wave flip-chip ICs (MFICs). They have significant advantages such as good performance, low cost and excellent flexibility in the active device selection which makes them superior to conventional monolithic microwave integrated circuits (MMICs). In order to demonstrate these advantages, a K-band front-end block for a broadband wireless communication equipment was designed and fabricated. This front-end block consists of four MFIC chips: a low noise amplifier (LNA), a down converter and two medium power amplifiers. These chips are designed to satisfy stable operation conditions using a simplified model derived for micro bump bonding (MBB). In experimental measurements; the LNA using heterojunction field-effect transistors (HFETs) had an 18 dB gain, the down converter using an HFET had a 9. 5 dB conversion loss, and two power amplifiers using heterojunction bipolar transistors (HBTs) had saturated powers of 13. 0 dBm and 11. 7 dBm, respectively. The performance for each of the developed ICs agreed with the designed values, and satisfied circuit requirements. These results show that the MFIC technique is a potential technology for manufacturing multi-functional millimeter-wave ICs.

We present ultra low noise- and wide dynamic range performances of an AlGaN/GaN heterostructure FET (HFET). An HFET fabricated on a high quality epitaxial layers grown on a semi-insulating SiC substrate exhibited impressively low minimum noise figure (NF min ) of 0.4 dB with 16 dB associated gain at 2 GHz. The low NF (near NF min ) operation was possible in a wide drain bias voltage range, i.e. from 3 V to 15 V. At the same time, the device showed low distortion character as indicated by the high third order input intercept point (IIP3), +13 dBm. The excellent characteristics are attributed to three major factors: (1) high quality epitaxial layers that realized a high transconductance and very low buffer leakage current; (2) excellent device isolation made by selective thermal oxidation; (3) ultra low gate leakage current realized by Pd based gate. The results demonstrate that the AlGaN/GaN HFET is a strong candidate for front-end LNAs in various mobile communication systems where both the low noise and the wide dynamic range are required.