Nobuhiro Kuwata

Pulse-doped GaAs MESFETs with planar self-aligned gate for MMIC

A pulse-doped GaAs MESFET with an n/sup +/ self-aligned planar gate has been developed. This device shows excellent drain current linearity and minimum noise figures of 0.72 dB (1.15 dB) with associated gains of 10.5 dB (8.5 dB) at 12 GHz (18 GHz). Furthermore, excellent uniformity and reproducible device characteristics have been realized.<<ETX>>

Low-noise characteristics of pulse-doped GaAs MESFETs with planar self-aligned gates

The authors report on the low-noise characteristics of pulse-doped GaAs MESFETs. The pulse-doped structure consists of an undoped GaAs buffer layer, a highly doped thin GaAs active layer, and an undoped GaAs cap layer grown by organometallic vapor phase epitaxy. Even though the electron mobility of this structure is 1500 cm/sup 2//V-s, the noise figures obtained are 0.72 dB at 12 GHz and 1.15 dB at 18 GHz. In addition, the noise figures are insensitive to the drain current. It was found that the noise characteristics improve as the active layer of the pulse-doped MESFET becomes thinner. These mechanisms can explain the cancellation effect between the drain noise current and gate-induced noise current as reported for HEMTs. >

X-band MMIC amplifier with pulse-doped GaAs MESFETs

An X-band monolithic low-noise amplifier (LNA) with 0.5- mu m-gate pulse-doped GaAs MESFETs was successfully demonstrated for a direct broadcast satellite (DBS) converter. This LNA shows excellent VSWR (voltage standing wave ratio) matches of under 1.4 as well as a noise figure of 1.67 dB and a gain of 24 dB at 12 GHz. The yield of chips within microwave specifications is 62.5%.<<ETX>>

MMIC family for DBS downconverter with pulse-doped GaAs MESFETs

An MMIC (monolithic microwave integrated circuit) family was demonstrated for a low noise block downconverter (LNB) for use in direct broadcast satellite (DBS) receivers operating from 11.7 to 12 GHz. A 12 GHz low noise amplifier, a 12 GHz mixer, a 10.7 GHz dielectric resonator oscillator and a 1 GHz IF amplifier were designed with 05 mu m-gate pulse-doped GaAs MESFETs. Noise-free pictured of satellite broadcast TV could be seen by using this LNB and a parabolic antenna forty centimeters in diameter.<<ETX>>

Electronic properties of a pulse‐doped GaAs structure grown by organometallic vapor phase epitaxy

A pulse‐doped GaAs structure was grown by organometallic vapor phase epitaxy using a conventional doping technique. Existence of a two‐dimensional electron gas confined in this structure was confirmed by Schubnikov–de Haas measurement. Electron mobility and concentration are evaluated by Hall measurement. Electron mobility and concentration dependence on temperature of a pulse‐doped GaAs are similar to those of a δ‐doped GaAs.

Ultra small sized low noise block downconverter module

A compact low-noise-block (LNB) downconverter module for use in direct broadcast satellite (DBS) reception utilizing only GaAs monolithic microwave integrated circuits (MMICs) has been successfully demonstrated. Four kinds of MMICs designed with 0.5- mu m-gate pulse-doped MESFETs were assembled in a miniaturized flat package (24.5 mm*17.8 mm*6.0 mm). 52-dB conversion gain and a 2.1-dB noise figure were obtained using no discrete high-electron-mobility transistors (HEMTs) in the preceding stage and no stub-tuning.<<ETX>>

X-band monolithic four-stage LNA with pulse-doped GaAs MESFETs

An X-band monolithic four-stage low-noise amplifier (LNA) with 0.5- mu m-gate pulse-doped GaAs MESFETs has been demonstrated. At 12 GHZ this LNA has a noise figure of 1.67 dB, with 18.5-dB gain, an input VSWR of less than 1.6:1, and an output VSWR of less than 1.8:1. Noise figure, gain, and VSWRs show very little bias current dependence due to the exceptional features of the pulse-doped structure FETs and the optimized circuit design. Insensitivity to bias current implies performance stability in the face of process fluctuations. Thus, high yield is obtained, making this device suitable for mass production.<<ETX>>

MMIC family for DBS down-converter with pulse-doped GaAs MESFETs

A monolithic microwave integrated circuit (MMIC) family was demonstrated as a low-noise block (LNB) downconverter for use in direct broadcast satellite (DBS) receivers operating from 11.7 to 12 GHz. A 12-GHz low-noise amplifier (LNA), a 12-GHz mixer (MIX), a 10.7-GHz dielectric resonator oscillator (DRO), and a 1-GHz IF amplifier (IFA) were designed with GaAs MMIC technology. These MMIC chips were designed to form a complete LNB downconverter function with the exception of the dielectric resonator. The most significant result of this work is that practical low-noise performance can be achieved without the use of high-electron-mobility transistors (HEMTs) in a preceding stage of the MMIC LNB downconverter. Almost noise-free satellite broadcast TV pictures were seen by using a parabolic antenna, 40 cm in diameter, without needing any additional circuit adjustment. >

Characterization of double pulse-doped channel GaAs MESFETs

The fabrication and characterization of a double pulse-doped (DPD) GaAs MESFET grown by organometallic vapor phase epitaxy (OMVPE) are reported. The electron mobility of a DPD structure with a carrier concentration of 3*10/sup 18//cm/sup 3/ was 2000 cm/sup 2//V-s, which is about 20% higher than that of a pulse-doped (PD) structure. Implementing the DPD structure instead of the conventional PD structure as a GaAs MESFET channel, the drain breakdown voltage, current gain cutoff frequency, and maximum stable gain (MSG) increase. The maximum transconductance of 265 mS/mm at a drain current density of 600 mA/mm, a current gain cutoff frequency of 40 GHz, and an MSG of 11 dB at 18 GHz were obtained for a 0.3 mu m n/sup +/ self-aligned DPD GaAs MESFET.<<ETX>>

A High Power and Low Distortion AlGaAs Hetero MESFET with a Graded Pulse-doped Channel for Base Station Applications

This paper reports on high power GaAs MESFET for base station applications, which has been improved over conventional GaAs MESFET in several aspects. High uniformity and high yield are achieved with a planar structure by using an n+ implantation and rapid thermal anneal (RTA) process rather than a recess process. Breakdown voltage and gate leak current are improved by the insertion of an AlGaAs-cap layer for usage in high drain voltage operations more than 10V. A graded pulse-doped channel is an active layer in which doping concentration increases exponentially toward the buffer layer, prevents output power deviation for bias drain current The AlGaAs hetero MESFET shows high gain (18dB), high output power (450mW/mm), and low intermodulation distortion (IP3=40dBm) at 1.9GH, which demonstrates excellent performance for digital wireless base station applications.