Marco Racanelli

Cryogenic operation of a 24 GHz MMIC SiGe HBT medium power amplifier

The performance of a SiGe heterojunction bipolar transistor (HBT) millimetre-wave power amplifier (PA) operating at cryogenic temperature was reported and analysed for the first time. A 24 GHz two-stage medium PA employing common-emitter and common-base SiGe power HBTs in the first and the second stage, respectively, showed a significant power gain increase at 77 K in comparison with that measured at room temperature. Detailed analyses indicate that cryogenic operation of SiGe HBT-based PAs mainly affects (improves) the performance of the SiGe HBTs in the circuits due to transconductance enhancement through magnified, favourable changes of SiGe bandgap due to cooling (ΔEg/kT) and minimized thermal effects, with little influence on the passive components of the circuits.

Power Performance Characteristics of SiGe Power HBTs at Extreme Temperatures

This paper presents the RF (6 GHz) power performance characteristics of SiGe power HBTs at cryogenic (77K) and high operation temperature (chuck temperature 120deg C, junction temperature up to 160degC). It shows that, without specific device optimizations for cryogenic operation, the power SiGe HBTs exhibit excellent large-signal characteristics at 77K. Comparing with room-temperature operation, similar power gain, output power and PAE were obtained when the devices were operated at the cryogenic temperature. The SiGe power HBTs also operate well at high junction temperature with reasonable power gain and output power degradations. The modeling of the SiGe power HBTs under high operation temperature indicates significant increase of base resistance (RB) and emitter resistance (RE) that account for the degradation of power performance of these devices.

Impact of Proton Radiation on the Large-Signal Power Performance of SiGe Power HBTs

The effects of proton irradiation on the RF power performance of SiGe power HBTs are, for the first time, reported in this work. Large emitter area high-power SiGe HBTs fabricated in a commercial BiCMOS process were irradiated with proton, at fluences up to 2times1013 p/cm2. Besides DC and small-signal AC characterizations, on-wafer large-signal high-power performance was characterized by load-pull measurements for pre- and post-radiation devices. It is shown that, in addition to DC and small-signal AC performance, the power performance of SiGe power HBTs also exhibits excellent tolerance to high-fluence proton radiations. Only a minor degradation (from the worst measurement case, 0.7 dB degradation in power gain, 8% degradation in PAE) was measured for post-radiation devices under class-AB bias at 1.9 GHz. Moreover, the source and load impedance matching points tuned for the optimum power performance of the devices, which are critical in the design of power amplifiers, are also shown to be robust to proton radiation. This work demonstrates the potential of SiGe power HBTs in the applications of power amplifiers for wireless application under severe radiation environment even without any intentional radiation hardening

SiGe power HBT design considerations for IEEE 802.11 applications

SiGe power HBTs integrated in SiGe BiCMOS are developed and characterized at 2.4 GHz for 802.11b and 5.8 GHz for 802.11a wireless LAN applications. Design considerations of ballast resistors for SiGe power HBTs at these two frequencies are investigated for both good thermal stability and high RF power performance. The investigations show that emitter ballast resistors or base ballast resistors should be judiciously used for SiGe power HBTs operating at different frequencies in order to extract the best RF performance from these devices. An RF output power of 30.8 dBm with PAE of 50.2 % at 2.4 GHz and an output power of 27.3 dBm with PAE of 23.6 % at 5.8 GHz are achieved from single discrete SiGe power HBTs with 0.4 /spl mu/m emitter width, respectively. These highest performance results demonstrate the great power amplification potential of SiGe HBTs for 802.11 wireless LAN applications.

Dc characteristics of proton radiated SiGe power HBTs at cryogenic temperature

The dc performances of proton irradiated silicon-germanium (SiGe) power heterojunction bipolar transistors (HBTs) at cryogenic temperature are reported in this work. Large emitter area high-power SiGe HBTs fabricated in a commercial BiCMOS process were irradiated with proton, at different fluences from 1×1012 p/cm2 to 5×1013 p/cm2. We show that proton radiated SiGe power HBTs are naturally suitable for electronic operations at cryogenic temperature. Specifically, investigation of proton radiation on SiGe power HBTs at liquid nitrogen temperature (77K) indicates a significant potential for space applications. The results demonstrate the potential of SiGe power HBTs in power amplification for wireless applications under severe radiation and extreme temperature environment (cryogenic) even without any intentional radiation hardening.

Assessment of influence of interconnect parasitics on RF Performance of multi-finger SiGe power HBTs

The influence of interconnect parasitics on the RF performance of large-area, multi-finger SiGe power HBTs is assessed. A new modeling approach is used to accurately modeling the interconnect parasitics of power devices and, furthermore, to accurately predicting the overall RF performance of the power devices. The validity of the approach is proved by the excellent agreement between simulations and measurement results obtained on multi-finger SiGe power HBTs of different sizes. It was found that the interconnect parasitics has dominant effects on the smalls-signal characteristics of SiGe power HBTs.

Impact of ballast resistor implementations on power performance of SiGe power HBTs

SiGe power HBTs integrated in SiGe BiCMOS with different ballast schemes are developed and compared in terms of large-signal power performance. Design considerations of ballast resistors for SiGe power HBTs are investigated for both common-emitter (CE) and common-base (CB) configurations. The investigation shows that emitter ballast resistors or base ballast resistors should be judiciously used for SiGe power HBTs operating at different frequencies and under different configurations in order to extract the best RF performance from these devices.

Effects of lateral scaling on power gain of multifinger SiGe power HBTs

The lateral scaling issues of high-power SiGe HBTs are analytically studied and verified using industry SiGe HBTs. It is found that due to increased parasitics in large-area power SiGe HBTs, fmax cannot be readily improved by only downscaling the emitter finger width. It is further found that without proper downscaling of the base stripe width, the maximum stable power gain (MSG) of power SiGe HBTs may be degraded by only shrinking the emitter finger width. It is thus proposed that both emitter finger width and the base stripe width ought to be downscaled properly in order to optimize the RF performance of SiGe power HBTs that are configured in a multiple subcell structure

A 0.1-14 GHz wideband SiGe BiFET power amplifier

In this paper, a wide bandwidth power amplifier, employing a MOS-HBT-HBT (BiFET) cascode as the unit section of distributed amplifier to provide improved output power as well as bandwidth, is designed. A four section distributed amplifier delivers a maximum output power of 22.8 dBm at 13 dBm input power, with -3 dB bandwidth of 13.9 GHz (0.1-14 GHz). The bandwidth and RF power achieved from this amplifier demonstrate that SiGe BiFET wideband power amplifiers have the potential to offer high performance for system-on-a-chip (SoC) integration

EXPERIMENTAL CHARACTERIZATION OF PROTON RADIATED SiGe POWER HBTs AT EXTREME TEMPERATURES

The performances of proton irradiated silicon–germanium (SiGe) power heterojunction bipolar transistors (HBTs) at extreme temperatures (liquid nitrogen temperature and high stage-temperature of 120°C with junction temperature over 160°C) are reported in this work. SiGe power HBTs with total emitter area of ~ 1460 μm2 are fabricated in a commercial BiCMOS process, and irradiated with proton at different fluences from 1 × 1012 p/cm2 to 5 × 1013 p/cm2. Experimental characterizations are conducted for pre- and post-radiation devices at room temperature, cryogenic temperature and high temperature. The results demonstrate that the proton-irradiated SiGe power HBTs are naturally suitable for electronic operations at extreme temperatures. Specifically, investigation of proton radiation on SiGe power HBTs at liquid nitrogen temperature (77 K) indicates a significant potential for space applications. In addition, SiGe power HBTs show better tolerance of proton radiation at high temperature of 120°C (junction temperature over 160°C). SiGe power HBTs demonstrate great potential in power amplification for wireless communication systems under severe radiation and extreme temperature environment (cryogenic and high temperatures) even without any intentional radiation hardening.