Hiroyuki Masato

In0.5Ga0.5As/InAlAs Modulation-doped Field Effect Transistors on GaAs Substrates Grown by Low-Temperature Molecular Beam Epitaxy

We report on the lattice-mismatched growth and electrical properties of In0.5Ga0.5As/InAlAs modulation-doped heterostructures on GaAs substrates by molecular beam epitaxy using a wide-gap InAlAs graded buffer layer and low-temperature Molecular Beam Epitaxial growth at about 350°C. A drastic reduction in residual carrier accumulation has been achieved, and a high electron mobility at room temperature of 11100 cm2/Vs was obtained with an electron concentration of 3×1012/cm2. It was found that the cause of residual carrier accumulation is related to the growth interruption or temperature rise after the growth of the graded buffer layer. The fabricated Modulation-doped Field Effect Transistors showed low output conductance, good pinch-off characteristics and no kink effect. The higher transconductance of 270 mS/mm was also obtained.

Self-aligned emitter power HBT and self-aligned gate power HFET for low/unity supply voltage operation in PHS handsets

Abstract A new power HBT and HFET were developed for low unity supply voltage operation in PHS handsets. The emitter region, the emitter electrode, the buried collector and the base electrodes in the power HBT are formed using the emitter electrode self-alignment process in order to reduce parasitic resistance and capacitance. The wirings on each electrode of the HBT are formed by Au plating technique for high current operation. The gate electrode in the power HFET is self-aligned to the drain/source electrodes by using the drain/source contact mesas as a mask, where the distance between the drain and the source is minimized and the parasitic resistances are reduced. In addition, an asymmetrical double-doped structure of AlGaAs/GaAs/InGaAs/AlGaAs is applied to the HFET in order to obtain a high current density. Both the power HBT and HFET exhibited the knee voltage less than 1 V with the maximum current more than 500 mA. The power HBT performed a power gain of 14.2 dB, an efficiency of 33.8% and the power HFET performed 12.5 dB and 34.5%, with a sufficient margin of distortion for PHS standard at an output power of 22 dBm, a supply voltage of 3.5 V and a frequency of 1.9 GHz under the unity operation.

AlGaAs/GaAs/InGaAs Double-Doped Quantum-Well HEMTs for Low Distortion Amplifier

We have successfully fabricated AlGaAVGaAVlnGaAs Double-Doped Quantum-Well (DDOVV) HEMTs with flat-gm charrcteristics in the wide gate vdtage range from -1.0V to 0.3V. The feedback amplifier using this HEMT showed excellent low distortion properties of lP. and lP. of 59.4dBm and 40.0dBm, respectively, at 1GHz, and good noise figure of less than 2.0d8 throughout a wide frequency range of 100MHz to 1 .6GHz. These features will make the DDQW HEMTs quite suitable for low-distortion and low-noise amplif ier applications.

Ohmic metal self-aligned gate power double-hetero FET for unity supply voltage operation in digital cellular

The objective of this work is to demonstrate a newly developed power HFET operable with low and unity supply voltage with a ohmic metal self-alignment FET process and an asymmetric double-hetero epitaxial structure. We have introduced a new self-alignment process to reduce parasitic resistances for low voltage operated power FETs, where the distance between the drain and the source has been minimized and consequently a knee voltage V/sub k/ in the I-V characteristics has been reduced. This newly developed FET was named OMEGA (ohmic metal self-aligned gate) FET. The results obtained indicate the new FET is highly suited for unity power applications and consequently contribute to minimize the battery cell and the size of microwave mobile communication handsets.