Nobuyuki Hayama

Emitter size effect on current gain in fully self-aligned AlGaAs/GaAs HBT's with AlGaAs surface passivation layer

The emitter size effect for fully self-aligned AlGaAs-GaAs heterojunction bipolar transistors (HBTs) with depleted AlGaAs passivation layers, in which the partially thinned AlGaAs emitter is self-aligned by using the dual sidewall process, is investigated. It is demonstrated that drastic improvement in the emitter size effect can be achieved with an AlGaAs passivation layer as small as 0.2 mu m in width, due to the surface recombination current reduction by a factor of 1/40 in the extrinsic base region. It has also been found that the base current is dominated by excess leakage current in the proton-implanted isolation region.<<ETX>>

1/f noise reduction in self-aligned AlGaAs/GaAs HBT with AlGaAs surface passivation layer

It is demonstrated that drastic improvement is achieved in base current noise for AlGaAs-passivated full self-aligned AlGaAs/GaAs HBTs, due to extrinsic base recombination current reduction. The base current 1/f noise was over 17 dB lower than that for an non-AlGaAs-passivated HBT, and comparable to that for an AlInAs/InGaAs HBT under a low collector density. >

Submicrometer fully self-aligned AlGaAs/GaAs Heterojunction bipolar transistor

A novel submicrometer fully self-aligned AlGaAs/GaAs heterojunction bipolar transistor (HBT) for reducing parasitic capacitances and resistances is proposed. The fabrication process utilizes SiO<inf>2</inf>sidewalls for defining base electrode width and separating this electrode from both emitter and collector electrodes. Measured common-emitter current gain β for a fabricated HBT with 0.6 × 10-µm²emitter dimension and 0.7 × 10-µm²× 2 base dimension is 26 at 9 × 10⁴-A/cm²collector current density.

A low-noise Ku-band AlGaAs/GaAs HBT oscillator

Design considerations, fabrication and performance results are described for a low-phase-noise Ku-band oscillator implemented using a fully self-aligned AlGaAs/GaAs heterojunction bipolar transistor (HBT). The transistor has a measured collector-current 1/f noise power density of 10/sup -19/A/sup 2//Hz at f=400 Hz for a collector current of 1.2 mA. The free-running oscillator developed represents an output power of 6 dBm at 15.5 GHz, with a single-sideband (SSB) FM noise of -65 dBc/Hz at 10 kHz off-carrier. The noise level is 24 dB lower than that for a GaAs FET oscillator, and 2 dB lower than that for a silicon voltage-controlled oscillator.<<ETX>>

Fully self-aligned AlGaAs/GaAs heterojunction bipolar transistors for high-speed integrated-circuits application

Structure optimization, uniformity consideration, and high-speed circuit performance for an AlGaAs/GaAs heterojunction bipolar transistor (HBT) are described. The HBT is fabricated in a fully self-alignment manner using only a single photoresist mask for achieving submicrometer-dimension devices, and, thus reducing parasitic elements. The fabricated HBTs exhibit excellent threshold voltage deviation sigma V/sub BE/=2 mV on a 2-in wafer, a CML gate propagation delay time tau /sub pd/=9.5 ps, and a toggle frequency f/sub tog/=13.3 GHz for a CML divide-by-two frequency divider. >

Gate length scaling for Al/sub 0.2/Ga/sub 0.8/N/GaN HJFETs: two-dimensional full band Monte Carlo simulation including polarization effect

Two-dimensional self-consistent full band Monte Carlo (FBMC) simulator was developed for electron transport in wurtzite phase AlGaN/GaN heterojunction (HJ) FET. Recessed gate Al/sub 0.2/Ga/sub 0.8/N/GaN HJFET structures with an undoped cap layer were simulated, where the spontaneous and piezoelectric polarization effects were taken into account. The polarization effect was shown to not only increase the current density, but also improve the carrier confinement, and hence improve the transconductance. An off-state drain breakdown voltage (BV/sub ds/) of 300 V and a maximum linear output power (P/sub max/) of 46 W/mm were predicted for a 0.9-/spl mu/m gate device. For a 0.1-/spl mu/m gate device, 60 V BV/sub ds/, 20 W/mm P/sub max/, and 160 GHz current-gain cutoff frequency were predicted. Although there is considerable uncertainty due to lack of information on the band structure, scattering rates, and surface conditions, the present results indicate a wide margin for improvements over current performance of AlGaN/GaN HJFETs in the future. To our knowledge, this is the first report on the FBMC simulation for AlGaN/GaN HJFETs.

High-efficiency, small-chip AlGaAs/GaAs power HBTs for low-voltage digital cellular phones

A 61% power added efficiency (PAE), high linearity AlGaAs/GaAs power HBT with a very small chip size of 0.58/spl times/0.77 mm for use in personal digital cellular phones (PDC) is described. The device layout is optimized to reduce thermal resistance while maintaining a compact chip size. This power HBT, which has 60 fingers of 2/spl times/30 /spl mu/m emitter, exhibited 31.4 dBm output power and 61% power added efficiency with -51.7 dBc adjacent channel leakage power at a 50 kHz offset frequency under 1.5 GHz /spl pi//4-shifted QPSK modulation when operated at a low collector-emitter voltage of 3.4 V. These results satisfy Japans PDC standard in a chip area that is less than 20% of that needed for a conventional GaAs power MESFET.

Submicron-square emitter AlGaAs/GaAs HBTs with AlGaAs hetero-guardring

Successful operation of submicron-square emitter AlGaAs/GaAs HBTs is demonstrated for the first time by using a fully mesa-structure-type emitter-base junction-area definition method with an AlGaAs hetero-guardring. The hetero-guardring reduces surface recombination current at the emitter-mesa edge to 1.4 /spl mu/A//spl mu/m. This is 1/10 of that for devices without the guardring. Here, dc gains of 20, 26, and 40 are achieved for 0.5 /spl mu/m/spl times/0.5 /spl mu/m, 0.7 /spl mu/m/spl times/0.7 /spl mu/m, and 0.9 /spl mu/m/spl times/0.9 /spl mu/m emitter HBTs, respectively. An f/sub T/ of 40 GHz, and an f/sub max/ of 30 GHz are obtained for 0.9 /spl mu/m/spl times/0.9 /spl mu/m at a J/sub C/ of 1.0/spl times/10/sup 5/ A/cm/sup 2/.<<ETX>>

A 0.08-cc fully integrated LTCC transceiver front-end module for 5-GHz wireless LAN systems

An extremely compact transceiver (TRx) front-end module (FEM) has been developed for 5-GHz wireless LAN systems. A highly-integrated flip-chip TRx IC and the embedding of passive devices in a low-temperature co-fired ceramic (LTCC) with high /spl epsi//sub r/(=17) are the keys to reducing the module size to 8 /spl times/ 10 /spl times/ 1 mm (0.08 cc). To the best of our knowledge, this is the most compact existing FEM that demonstrates full transceiver operation and complies with the IEEE 802.11a standard.

High-linearity and small-chip AlGaAs/GaAs power HBTs for L-band personal digital cellular applications

A high-linearity AlGaAs/GaAs power heterojunction bipolar transistor (HBT) is developed for personal digital cellular phones. For compact chip layout, thermal design was considered. To improve power performance, proton implantation, optimum alloy condition for collector electrodes, and multiple via holes were used. A 2400-/spl mu/m/sup 2/-emitter-area HBT fabricated on a 0.5/spl times/0.67 mm/sup 2/ substrate exhibits adjacent channel leakage powers below -53 dBc for 0.95- and 1.5-GHz /spl pi//4-shifted QPSK modulated input signals at a low collector-emitter voltage of 3.4 V. The HBT produces a 31.7-dBm output power, 50% power-added efficiency, and 15-dB linear power gain at 0.95 GHz, and produced a 31.3-dBm output power, 52% power-added efficiency, and 11.5-dB linear power gain at 1.5 GHz. These results were achieved on about one-fifth of the substrate area of conventional GaAs FETs.