Kazuhiko Honjo

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>>

High-f/sub max/ AlGaAs/InGaAs and AlGaAs/GaAs HBT's with p/sup +//p regrown base contacts

The present paper describes a new approach to fabricating high performance HBTs with low base resistance. Their base contact resistance is reduced by using MOMBE selective growth in the extrinsic base region-a key process in the fabrication of high-f/sub max/ AlGaAs/InGaAs and AlGaAs/GaAs HBTs. A p/sup +//p regrown base structure, which consists of a 40-nm-thick graded InGaAs strained layer and a heavily C-doped regrown contact layer, is used for the AlGaAs/InGaAs HBTs to reduce both their base transit time and base resistance, while preventing aluminum oxide incorporation at the regrowth interface. An h/sub fe/ of 93, an f/sub T/ of 102 GHz, and an f/sub max/ of 224 GHz are achieved for a 1.6-/spl mu/m/spl times/4.6-/spl mu/m HBT, together with reduced base push-out effects and improved reliability. AlGaAs/GaAs HBTs with an 80-nm-thick uniform base layer that have high f/sub max/ values ranging from 140-216 GHz are also fabricated using the selective growth technique. These results confirm the high potential of the proposed HBTs, especially for microwave and millimeter-wave applications. >

A simple circuit synthesis method for microwave class-F ultra-high-efficiency amplifiers with reactance-compensation circuits

Abstract A class-F amplifier circuit by which the transistor load impedance, for even-order higher harmonics, can be kept “zero” and that for odd-order higher harmonics can be kept “open” without affecting the impedance at the fundamental frequency has been developed. This circuit basically consists of transmission lines with lengths equal to a half wavelength and a quarter wavelength at the fundamental frequency where the residual reactance at the fundamental frequency, due to the higher harmonic-frequency circuits, is compensated. Using this circuit, a microwave heterojunction bipolar transistor amplifier was designed using a harmonic-balance simulator. The designed power-added efficiency was more than 90%. The output waveforms, a dynamic load line, and the input/output power response were evaluated.

Characterization of current-induced degradation in Be-doped HBTs based in GaAs and InP

The changes in the device characteristics under high-bias conditions are investigated for InAlAs/InGaAs and AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with heavily Be-doped base lasers, focusing on the base current and 1/f noise characteristics. It is shown that the ideality factor of the surface recombination base current provides information on the Be movement accompanying the degradation. For stress current densities up to 1.5*10/sup 5/ A/cm/sup 2/, the Be movement in the InAlAs/InGaAs HBTs is estimated to be no more than a small fraction of the 5 nm setback layer. The 1/f noise measurement highlight the effect of current stressing on the surface recombination in the HBTs. A characteristic spectral shape is found in the noise spectra for the current-stressed AlGaAs/GaAs HBT, possibly originating from the degradation-induced carrier traps. Although both HBTs have similar electronic properties, these results illustrate the striking difference in their stress current behaviors. >

50-GHz bandwidth base-band amplifiers using GaAs-based HBTs

Base-band amplifiers have been demonstrated using AlGaAs/InGaAs HBTs with regrown base contacts. The transimpedance amplifier achieved a bandwidth of 49.3 GHz and a transimpedance gain of 43.7 dB /spl Omega/. The Darlington feedback amplifier achieved a bandwidth of 54.7 GHz and a gain of 8.2 dB. These are the widest bandwidths yet reported for lumped-circuit-design amplifiers. These performances suggest the great potential of these amplifiers for use in future optical communication and millimeter-wave applications.

Group Delay Equalized UWB InGaP/GaAs HBT MMIC Amplifier Using Negative Group Delay Circuits

A negative group delay (NGD) circuit has been employed to equalize a group delay variation in a broadband ultra-wideband (UWB) InGaP/GaAs heterojunction bipolar transistor (HBT) monolithic microwave integrated circuit (MMIC) amplifier. Using the NGD circuit, a part of a salient group delay characteristic in the operation band of broadband amplifiers can be suppressed without an increase of the entire group delay. The MMIC amplifier has a steep group delay increase in the lower frequency region of the full-band UWB band (3.1-10.6 GHz) due to the sum of phase variations near the cutoff frequencies of the HBTs. The NGD circuit has been inserted to reduce this increase of the group delay in the UWB band. By adding a three-cell NGD circuit while considering input and output matching at the input side of the MMIC amplifier, the group delay variation is decreased by 78%. However, gain was also decreased by insertion of the multistage NGD circuit. In an attempt to avoid this decrease in gain, a one-cell NGD circuit was inserted into the feedback loop of the MMIC amplifier, and as a result, we were able to decrease the group delay variation by 79%, with minimal gain deterioration.

Ultra-Wideband, Differential-Mode Bandpass Filters with Four Coupled Lines Embedded in Self-Complementary Antennas

SUMMARY A design method for an ultra-wideband bandpass filter (BPF) with four coupled lines has been developed. For demonstration purposes, 50 Ω-matched self-complementary antennas integrated with the ultra-wideband, differential-mode BPF with four coupled lines, a notch filter, and a low-pass filter (LPF) were prepared and tested. An optimized structure for a single-stage, broadside-coupled and edge-coupled four-lines BPF was shown to exhibit up to 170% fractional bandwidth and an impedance transformation ratio of 1.2 with little bandwidth reduction, both analytically and experimentally. Using the optimized structure, 6stage BPFs were designed to transform the self-complementary antenna’s constant input impedance (60πe −1/2 e (Ω)) to 50 Ω without degrading bandwidth. In addition, two types of filter variations — a LPF-embedded BPF and a notch filter-embedded BPF — were designed and fabricated. The measured insertion loss of both filter systems was less than 2.6 dB over the ultra-wideband (UWB) band from 3.1 GHz to 10.6 GHz. The filter systems were embedded in the wideband self-complementary antennas to reject un

Practical realization of self-complementary broadband antenna on low-loss resin substrate for UWB applications

Practical realizations of self-complementary ultra-wideband antennas on low-loss resin materials are demonstrated. Dependences of broadband characteristics on sizes and shapes are clarified by simulations and experiments. The self-complementary antennas impedance-matched to a 50-ohm system, utilizing a 3-stage Chebyshev transformer over the UWB band, were designed and fabricated on a resin material (the relative permittivity; /spl epsiv//sub r/=3.6). A measured return loss of less than -9.8 dB and a measured absolute gain of 0-3 dBi over a frequency range from 3.1 to 10.6 GHz (the UWB band) were obtained with a 30 mm/spl times/60 mm sized antenna. A reduced sized antenna (20 mm/spl times/40 mm), designed and fabricated on a resin material of /spl epsiv//sub r/=10.2, delivered a return loss of less than -7.8 dB with an isotropic radiation pattern.

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. >

GaAs Fet Ultrabroad-Band Amplifiers for Gbit/s Data Rate Systems

A novel ultrabroad-band amplifier configuration suitable for GaAs FETs has been developed. The developed amplifier circuit operates as a capacitor-resistor ( C-R ) coupled mnpfifier circuit in the low-frequency range in which |S/sub 21/| for the GaAs FETs is constant. It also operates as a lossless impedance matching circuit in the microwave frequency range in which |S/sub 21/| for the GaAs FET has a slop of approximately -6 dB/octave. Using this configuration technique, 800-kHz 9.5-GHz band (13.5 octaves), 8.6-dB gain GaAs FET amplifier modules have been realized. The amplifier module has 40-ps step response rise time. It also has low input and output VSWR. By cascading two-amplifier modules, 19-dB gain over the 800-kHz to 8.5-GHz range and 50-ps step response rise time were obtained. NF is lower than 8 dB over the 50-MHz to 6-GHz range.