M. Borgarino

Hot electron degradation of the DC and RF characteristics of AlGaAs/InGaAs/GaAs PHEMT's

This paper reports on hot electron (HE) degradation of 0.25-/spl mu/m Al/sub 0.25/Ga/sub 0.75/As/In/sub 0.2/Ga/sub 0.8/As/GaAs PHEMTs by showing the effects of the hot electron stress on both the dc and rf characteristics. The changes of dc and rf behavior after stress turn out to be strongly correlated. Both can be attributed to a decrease of the threshold voltage yielding different effects on the device gain depending on the bias point chosen for device operation and on the bias circuit adopted: a fixed current bias scheme will minimize the changes induced by the stress. The work also presents a study of the dependence of device degradation on the stress bias condition.

On the effects of hot electrons on the DC and RF characteristics of lattice-matched InAlAs/InGaAs/InP HEMTs

The authors for the first time present results of hot electron stressing of InAlAs/InGaAs/InP high electron mobility transistors (HEMTs). High drain bias, room temperature stress cycles have been applied to 0.3 μm, SiN-passivated, lattice-matched devices, and the changes of the DC and RF (up to 50 GHz) characteristics have been studied. Both the DC and RF device gain degrade after stressing; the effect of the stress on the unity current gain cutoff frequency fT is studied under different bias conditions. Results indicate that surface degradation may be responsible for the observed changes.

Influence of surface recombination on the burn-in effect in microwave GaInP/GaAs HBT's

In this paper, we report on the early increase of the dc current gain (burn-in effect) due to the electrical stress of carbon doped GaInP/GaAs heterojunction bipolar transistors (HBTs). Devices featuring different passivation layers, base doping, and emitter widths were investigated. The obtained data demonstrate that the burn-in effect is due to a reduction of the surface recombination located at the extrinsic base surface, around the emitter perimeter. It is concluded that the recombination centers are related to defects at the passivation/semiconductor interface and that, during the stress, they are passivated by hydrogen atoms released from C-H complexes.

Reliability physics of compound semiconductor transistors for microwave applications

Abstract This paper reviews the reliability problems of compound semiconductor transistors for microwave applications. These devices suffer from specific failure mechanisms, which are related to their limited maturity, with the exception of the GaAs MESFETs, which exhibit a stable technology and an assessed reliability. The metallizations employed in high electron mobility transistors (HEMTs) already benefit from this assessment. However, HEMT are affected by concerns related to hot carriers and impact ionization. The trapping of carriers and the generation of defects in the different layers are responsible for the observed instabilities. The stability of the base dopant is the main reliability concern for heterojunction bipolar transistors (HBTs). Beryllium outdiffuses from the base into the emitter and causes device degradation. Carbon has a lower diffusivity, but is affected by the presence of hydrogen, which prompts gain variations. Finally the hot carriers reliability concern in SiGe HBTs is briefly reviewed.

Transimpedance amplifier-based full low-frequency noise characterization setup for Si/SiGe HBTs

An experimental setup, based on current/voltage conversion through transimpedance amplifiers (TAs), has been implemented for the direct full low-frequency noise (LFN) characterization of Si/SiGe heterojunction bipolar transistors (HBTs) in terms of base and collector short-circuit current noise sources. This setup performs a full characterization, as it measures simultaneously the two noise current sources and their correlation, thanks to an original technique based on the specific properties of a specially designed buffer amplifier using a low-noise common-base bipolar transistor (CB BJT). By means of translation formulae, the obtained measurements are compared with those carried out with a multi-impedance technique. They show a good agreement both for the noise sources spectral densities and for their correlation. The TA-based setup provides enhanced capabilities in terms of measurement speed and remote control potentialities.

On the correlation between drain-gate breakdown voltage and hot-electron reliability in InP HEMTs

By comparing devices with different recess widths, we show that the off-state drain-gate breakdown voltage (BV/sub DG/) may give totally misleading indications on the reliability of lattice-matched InP HEMTs under hot-electron (HE) and impact ionization conditions, from both standpoints of gradual and catastrophic degradation. Since the hot-electron degradation effects observed in our HEMTs are quite common, we believe that our results should be considered as a general caveat whenever indications on HE HEMT robustness are inferred from BV/sub DG/ measurements.

Dynamic thermal characterization and modeling of packaged AlGaAs/GaAs HBTs

In this work we show a method for the thermal dynamic modeling of packaged HBTs. The method employs a calibration step featuring pulsed measurements at different temperatures, and is based upon a 3-stage thermal resistance-capacitance model that describes the chip-solder-case system. A current pulse generator was designed and assembled in-house for pulsed characterization down to the microsecond range. The model was used to simulate the thermal transients of the collector current from the microsecond range to hundreds of seconds, for several different bias points in the forward active region, consistently showing a good match with the measured characteristics.

An Empirical Bipolar Device Nonlinear Noise Modeling Approach for Large-Signal Microwave Circuit Analysis

An empirical bipolar transistor nonlinear noise model for the large-signal (LS) noise analysis of microwave circuits is described. The model is derived according to the charge-controlled nonlinear noise behavioral modeling approach, and includes nonlinearly controlled equivalent noise (EN) generators describing the low-frequency (LF) noise up-conversion encountered in LS RF operation. LS-modulated shot-noise sources and parametric LF noise in parasitic resistors are also taken into account for improved model accuracy. Details for the implementation of the proposed cyclostationary EN generators in the framework of a computer-aided design tool are presented. As an application example, a simplified version of the proposed nonlinear noise model for two GaInP-GaAs HBTs has been formulated and empirically characterized on the basis of both bias-dependent LF noise and phase-noise measurements. Measured and simulated noise performance of a monolithic voltage-controlled oscillator over a set of different operating conditions is shown for the validation of the proposed approach

System-on-chip microwave radiometer for thermal remote sensing and its application to the forest fire detection

This paper focuses on the opportunities offered by the latest advances in silicon technologies for realizing system-on-chip microwave radiometer. Such a highly integrated, low-cost, radiometer chip could be applied to the environmental remote sensing and, in particular, to the forest fire detection. The feasibility study is carried-out in two steps. First, a proof of the concept is given by means of a discrete-component radiometer operating at 12.65 GHz. This radiometer exploits TV-SAT components such as low-noise down-converter and dish antenna. On-field measurements shows a radiometric contrast (increase of the antenna noise temperature due to the fire with respect to the background) of about 8 K for a wooden fire of 0.38 m 2 placed 30 m away from the antenna. Then, a single-chip 13 GHz radiometer has been designed exploiting a CMOS 90 nm standard process. The sensor is based on a direct-conversion architecture with integrated LNA, Gilbertpsilas cell mixer and PLL frequency synthesizer. The IF chain includes an active (gm-C) low-pass filter and a CMOS square-law detector. The circuit simulations show a total receiver gain of 72 dB, an equivalent input noise temperature of 105 K and an IF bandwidth of 100 MHz.

Noise behavior in SiGe devices

Abstract This paper presents an overview of SiGe technologies and their corresponding noise properties both in the high frequency and low frequency range. We demonstrate that SiGe bipolar technology exhibits impressive low frequency noise performance with an excess corner noise frequency in the 1 kHz range. These results have been validated by low phase noise microwave oscillators based on SiGe material.