Effects In Heterojunction Bipolar Transistors Research Articles

Study on ionization damage of silicon-germanium heterojunction bipolar transistors at various dose rates

Ionizing radiation effects in silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) at different dose rates were investigated. Experimental results show that the base current increases with increasing accumulated dose for the high and low dose rates of irradiation, causing a significant drop in current gain. Besides, the lower the dose rate, the higher the radiation damage, which demonstrates a significantly enhanced low-date-rate sensitivity (ELDRS) effect in the SiGe HBTs. The different degradation behaviors for high and low dose rates of irradiation are compared with each other and discussed; furthermore, the underlying physical mechanisms are analyzed and investigated in detail.

A Novel Model for Implementation of Gamma Radiation Effects in GaAs HBTs

For predicting the effects of gamma radiation on gallium-arsenide (GaAs) heterojunction bipolar transistors (HBTs), a novel model is presented in this paper, considering the radiation effects. Based on the analysis of radiation-induced degradation in forward base current and cutoff frequency, three semiempirical models to describe the variation of three sensitive model parameters are used for simulating the radiation effects within the framework of a simplified vertical bipolar inter-company model. Its validity was demonstrated by analysis of the experimental results of GaAs HBTs before and after gamma radiation.

A Scalable Electrothermal Model for Transient Self-Heating Effects in Trench-Isolated SiGe HBTs

This paper demonstrates a scalable electrothermal model for transient self-heating effects in trench-isolated SiGe heterojunction bipolar transistors (HBTs). The scalability of the thermal model has been investigated by considering pyramidal heat diffusion approximation between the heat source and the thermal ground. Three-dimensional thermal TCAD simulations have been carried out to obtain transient variations of the junction temperature and to extract the thermal impedance in the frequency domain. A recursive thermal network with scalable model parameters has been developed and added at the temperature node of the HBT compact model HiCuM. This network has been verified through numerical simulations and by low-frequency <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$s$</tex></formula> -parameter measurements and found to be in excellent agreement for various device geometries.

A review of radiation effects in heterojunction bipolar transistors

We present a review of radiation effects studies on heterojunction bipolar transistors (HBTs) in order to develop a framework for qualifying devices for application in the harsh radiation environment of space. Radiation effects in different HBT material systems are considered here, including Si/SiGe, GaAs/AlGaAs, and InP/InGaAs. We discuss the different effects of ionizing and nonionizing radiation on device performance and review the strong role that device geometry plays in determining the overall radiation tolerance. We present a new comparison of radiation tolerance in conventional transistors, HBTs, and high electron mobility transistors. Finally, we conclude that with proper design, HBTs are excellent candidates for application in space.

The effect of vertical emitter ballasting resistors on the emitter current crowding effect in heterojunction bipolar transistors

In order to improve thermal stability and extend their safe operation region, epitaxial emitter ballasting resistors have been incorporated into power heterojunction bipolar transistors (HBTs). In this report, we show that this lightly doped layer not only can function as ballasting resistors used in multi-finger power HBT cells, but also can reduce the emitter current crowding effect which is an important limitation in bipolar transistors operating at high emitter current densities.

An analytical model of the inverse base width modulation effect in SiGe graded heterojunction bipolar transistors

The analytical model of the collector current ideality factor degradation at high V be in modern SiGe graded base heterojunction bipolar transistors (HBTs) has been developed for the first time. It is subsequently used for the analysis of the inverse base width modulation (IBWM) effects in SiGe HBTs with respect to collector current degradation, current gain premature roll-off and SiGe base transit time. Comparing the IBWM effects calculated for HBTs with various base impurity concentration doping profiles and the Ge grading, we have found that the careful optimization of SiGe base parameters may substantially minimize negative influence of the IBMW effects on the HBT electrical parameters.

MBE grown vertical emitter ballasting resistors to reduce the emitter current crowding effect in heterojunction bipolar transistors

In order to improve thermal stability and extend their safe operation region, epitaxial emitter ballasting resistors have been incorporated into power heterojunction bipolar transistors (HBTs). In this report, we show that this lightly doped layer not only can function as ballasting resistors used in multi-finger power HBT cells, but also can reduce the emitter current crowding effect which is an important limitation in bipolar transistors operating at high emitter current densities.

High-injection barrier effects in SiGe HBTs operating at cryogenic temperatures

We demonstrate that high-injection barrier effects associated with the collector-base silicon-germanium (SiGe) to silicon (Si) heterojunction are an important design constraint for SiGe heterojunction bipolar transistors (HBTs) operating at cryogenic temperatures. Due to its thermally activated nature, these barrier effects can have important dc and ac consequences at cryogenic temperatures even when undetectable under room temperature operation. We use measured results from advanced SiGe HBTs and Si BJTs over a wide temperature range, in combination with simulation, to shed light on the design issues associated with these high-injection barrier phenomena

Dynamic Early effect in heterojunction bipolar transistors

A theory of base transport in an abrupt-junction heterostructure bipolar transistor (HBT) is developed in the diffusion limit. The theory is valid for a continuous range of emitter injection energies Delta and accounts for the Early effect in both the static and the high-frequency limits. Small-signal network parameters strongly depend on Delta and differ from those in a graded emitter-base junction HBT.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Investigation of emitter current crowding effect in heterojunction bipolar transistors

The emitter current crowding effect in heterojunction bipolar transistors (HBTs) has been investigated using a specific test device. This test device, which is a heterojunction bipolar transistor with two separate base fingers, also allows evaluation of the HBT base resistance. By use of this test device, the Letter demonstrate that a 3μm large HBT does not exhibit the emitter current crowding effect. An analysis of the saturated regime is also presented.