Forward-active Region Research Articles

96 GHz 4.7 mW low‐power frequency tripler with 0.5 V supply voltage

Using forward-biased base–collector voltage (VBC) in high-speed circuits is usually not attractive due to the performance degradation compared with biasing heterojunction bipolar transistors (HBTs) in the forward-active region. However, the use of ultra-low supply voltage in millimetre-wave circuits provides an interesting application scenario not only for demonstrating the potential of modern silicon germanium (SiGe) HBT technologies in implementing severely power-constrained wireless circuits on silicon but also for verifying the accuracy of compact models beyond standard characteristics typically measured by foundries. The results of a 96 GHz frequency tripler deliberately designed with a reduced supply voltage (0.5 V) in a 130 nm SiGe HBT technology are presented. With only 4.7 mW DC power consumption, this frequency tripler achieves a conversion loss of 3.8 dB, generating a 96 GHz output signal with only −10 dBm input signal at 32 GHz. The impact of transistor series resistances on the tripler performance is also analysed.

그래핀을 베이스로 사용한 열전자 트랜지스터의 특성

Graphene has a monolayer crystal structure formed with C-atoms and has been used as a base layer of HETs (hot electron transistors). Graphene HETs have exhibited the operation at THz frequencies and higher current on/off ratio than that of Graphene FETs. In this article, we report on the preliminary results of current characteristics from the HETs which are fabricated utilizing highly doped Si collector, graphene base, and 5 nm thin tunnel layers between the base and Ti emitter. We have observed E-B forward currents are inherited to tunneling through layers, but have not noticed the Schottky barrier blocking effect on B-C forward current at the base/collector interface. At the common-emitter configuration, under a constant between 0~1.2V, has increased linearly with for indicating the saturation region. As the increases further, a plateau of vs. has appeared slightly at , denoting forward-active region. With further increase of , has kept increasing probably due to tunneling through thin Schottky barrier between B/C. Thus the current on/off ration has exhibited to be 50. To improve hot electron effects, we propose the usage of low doped Si substrate, insertion of barrier layer between B/C, or substrates with low electron affinity.

The damage effect and mechanism of bipolar transistors induced by injection of electromagnetic pulse from the base

A two-dimensional electrothermal model of the bipolar transistor (BJT) is established, and the transient behaviors of the BJT originally in the forward-active region are simulated with the injection of electromagnetic pulse from the base. The results show that the damage location of the BJT shifts with the amplitude of the pulse. With a low pulse amplitude, the burnout of the BJT is caused by the avalanche breakdown of the emitter-base junction, and the damage location lies in the cylindrical region of this junction. With a high pulse amplitude, the damage first occurs at the edge of the base closer to the emitter due to the second breakdown of the p-n-n+ structure composed of the base, the epitaxial layer and the substrate. The burnout time increases with pulse amplitude increasing, while the damage energy changes in a decrease-increase-decrease order with it, thus generating both a minimum value and a maximum value of the damage energy. A comparison between simulation results and experimental ones shows that the transistor model presented in the paper can not only predict the damage location in the BJT under intense electromagnetic pulses, but also obtain the damage energy.

Investigation of an InGaP/GaAs resonant-tunneling transistor (RTT)

A new InGaP/GaAs resonant-tunneling transistor (RTT) has been fabricated successfully and demonstrated. A 5-period InGaP/GaAs superlattice is used as a confinement barrier for holes and an RT route for electrons. A transistor action with a common-emitter current gain up to 220 and an offset voltage of 85 mV are obtained. Due to the RT effect within the 5-period superlattice near the emitter–base p–n junction region, the N-shaped negative-differential-resistance (NDR) phenomena are observed at room temperature. Furthermore, the N-shaped NDR is found both in the saturation and forward-active region. The widely operating regime of NDR may provide the potential for practical applications.

InGaP/GaAs superlattice-emitter resonant tunneling bipolar transistor (SE-RTBT)

In this letter, a new InGaP/GaAs superlattice-emitter resonant tunneling bipolar transistor (SE-RTBT) is fabricated and demonstrated. A 5-period InGaP/GaAs superlattice is used to serve the RT route and the confinement barrier for minority carriers. Due to the large valence band discontinuity (/spl Delta/E/sub v/) at the InGaP/GaAs heterointerface, a high current gain (/spl beta//sub max//spl sime/220) is obtained. Furthermore, the interesting N-shaped negative-differential-resistance (NDR) phenomena resulting from RT effect are found both in the saturation and forward-active region of current-voltage (I-V) characteristics at room temperature.

Transient latchup in bulk CMOS with a voltage-dependent well-substrate junction capacitance

Transient latchup in bulk CMOS with a voltage-dependent well-substrate junction capacitance under a voltage ramp is analyzed. It is found that even when the external voltage is ramping up, α <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> + α <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> > 1, and both bipolar transistors are biased in the forward-active region, the circuit can still dynamically recover internally due to the inherently nonlinear character of the voltage-dependent substrate-well junction capacitance. Numerical results for the cases of linearly graded and step junctions are presented and some optimal conditions for preventing transient latchup are briefly discussed.

‘Early-intercept voltage’: a parameter of voltage-driven b.j.t.s

Experimental measurements support a theoretical argument suggesting that if the collector current of a b.j.t. is plotted against collector-base voltage, for set values of base-emitter drive voltage, then the tangents to the characteristics at a given collector-base voltage, in the forward-active region, have a common intersection point on the collector-base voltage axis. The usefulness of this parameter, designated the early-intercept voltage, in the analysis of some linear i.e. schemes is mentioned.