High-frequency operation with ultrathin, lightweight, and extremely flexible semiconducting electronics is highly desirable for the development of mobile devices, wearable electronic systems, and defense technologies. In this work, the experimental observation of quasi-heterojunction bipolar transistors utilizing a monolayer of the lateral WSe2–MoS2 junctions as the conducting p–n channel is demonstrated. Both lateral n–p–n and p–n–p heterojunction bipolar transistors are fabricated to exhibit the output characteristics and current gain. A maximum common-emitter current gain of around 3 is obtained in our prototype two-dimensional quasi-heterojunction bipolar transistors. Interestingly, we also observe the negative differential resistance in the electrical characteristics. A potential mechanism is that the negative differential resistance is induced by resonant tunneling phenomenon due to the formation of quantum well under applying high bias voltages. Our results open the door to two-dimensional material...

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Atomic-Monolayer Two-Dimensional Lateral Quasi-Heterojunction Bipolar Transistors with Resonant Tunneling Phenomenon

This paper discusses the effects of process and temperature variations on the performance of GaAs HBT power amplifier bias circuits. A novel feedback bias circuit, which overcomes these problems, is presented. The measured variation from 54 to 60 mA in the bias current, over the temperature range of -25 to +85/spl deg/C, agrees well with the simulations. The circuit is insensitive to variations in the regulated voltage which is a desirable feature in a case when the amplifier is biased to a constant current. On the other hand, a smooth bias and gain control can be achieved by adding an extra resistor connected to a separate control voltage.

Bias circuits for GaAs HBT power amplifiers

This paper describes what is believed to be the first full two-dimensional electroluminescent (EL) analysis of base-emitter junctions in heterojunction bipolar transistors (HBTs). Correlation of the DC and RF characteristics with respect to the changes in EL emission are presented. Special sample preparation techniques and emission microscopy procedures were used to reveal the full electroluminescent pattern from the backside of discrete HBT chips. Sample mounting was optimized to permit inspection at a magnification of 500/spl times/. Two parallel emitter fingers, 3 /spl mu/m by 10 /spl mu/m each, were easily resolved. This technique is utilized to investigate HBT susceptibility to current driven lattice degradation that manifests itself in nonradiative recombination regions. Occurrence of dark line defects (DLDs) is similar to that reported for solid state lasers and light emitting diodes (LEDs). Rapid changes in the EL pattern occur at current densities of 150 kA/cm/sup 2/. Full two-dimensional electroluminescent analysis represents a breakthrough in the investigation and resolution of current driven degradation in HBT devices because dramatic changes in the optical characteristics occur prior to small changes in the electronic characteristics.

Full two-dimensional electroluminescent (EL) analysis of GaAs-AlGaAs HBTs

In this paper, the recent advances of CDMA power amplifier module developments for wireless handset applications are reviewed Technology choices among GaAs, SiGe and PHEMT for linear PA designs are compared The trade-offs of circuit design and module approaches are discussed in detail The measured performances of some representative state of the art power amplifier modules are presented The high integration of more front-end components and functionalities into the power amplifier module and the increasing demand for high linear efficiency at lower output power has become a widely acceptable trend

Recent advances in CDMA power amplifier module developments

Medium power transistors in a high performance double polysilicon bipolar process have been fabricated. On-wafer loadpull measurements show high gain (15 dB) and high maximum efficiency (60%) at 1.8 GHz with 27 dBm of output power. These results were obtained with a low supply voltage of 3.5 V. More importantly, these results were obtained with transistors with a buried layer having a collector contact at the top, which makes it possible to integrate power amplifiers on chip.

High gain, high efficiency, low voltage, medium power Si-bipolar transistor suitable for integration

This paper provides a synopsis of the research and development efforts in the USA in power amplifiers designed with GaAs Heterojunction Bipolar Transistor (HBT) technology. Design issues, performance and reliability of power amplifiers using AlGaAs/GaAs HBTs for RF, microwave and millimeter-wave applications are discussed. Key device parameters influencing different frequency applications are highlighted.

F. Ali

Papers

Advances in GaAs HBT power amplifiers for cellular phones and military applications