Base Push-out Effect Research Articles

Base charge accumulation and push-out effects on nonlinearity of Type-I InP/InGaAs/InP and Type-I/II AlInP/GaAsSb/InP double heterojunction bipolar transistors

The influence of energy band alignment on carrier transport and signal integrity is investigated on fabricated Type-I InP/InGaAs/InP and Type-I/II AlInP/GaAsSb/InP DHBTs. The Type-I double heterojunction bipolar transistor (DHBT) requires the use of a transition region (setback and superlattice layer) in base-collector hetero-interface to minimize the conduction band discontinuity that can cause current blocking in the collector I-V characteristics. Despite the effort, Type-I DHBT exhibits gain compression and base charge accumulation at high current injection, giving a nonlinear microwave operation. In contrast, the Type-I/II DHBT has a favorable band alignment and permits hot electron injection without impedance in both emitter-base and base-collector junctions, resulting in considerable microwave linearity improvement.

Part I: On the Behavior of STI-Type DeNMOS Device Under ESD Conditions

We present experimental and simulation studies of shallow trench isolation (STI)-type drain-extended n-channel metal-oxide-semiconductor devices under human body model (HBM)-like electrostatic discharge (ESD) conditions. Physical insight toward pulse-to-pulse instability is given. Both the current ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TLP</sub> ) and time evolution of various events such as junction breakdown, parasitic bipolar triggering, and the base push-out effect are discussed in detail. Differences between the 2-D and 3-D simulation (modeling) approaches are presented, and the importance of 3-D technology-computer-aided-design-based modeling is discussed. Furthermore, a deeper physical insight toward the base push-out is given, which shows significant power dissipation due of space charge build-up, which is found at the onset of self-heating in the 2-D plane.

Harnessing the base-pushout effect for ESD protection in bipolar and BiCMOS technologies

The impact of the base-pushout or Kirk-effect on the ESD characteristic of modern radio frequency (RF) NPN transistors is investigated. Due to the RF NPNs selectively implanted collector the onset of base-pushout is shifted to ESD relevant current levels, expressing itself in a characteristically high-ohmic breakdown mode after first snapback and a non-thermal second snapback, the so-called current mode snapback. Concepts to exploit the base-pushout effect for improved RF protection schemes are presented.

An improved electron current model of AlGaAs/GaAs HBTs including self-heating effects

An improved electron current model of graded heterojunction AlGaAs/GaAs HBTs is presented to account for the effect of varied electron quasi-Fermi level from the emitter region to the base region, the base push-out effect and the self-heating effect. For the self-heating effect, two kinds of thermal boundary conditions in one dimension are included, which are heat insulation at the emitter contact and fixed temperature at the collector contact and the reverse case. In each boundary condition, the more accurate b-e junction temperature model is established, and incorporated into the electron. current formula to form the combined model. A comparison of this model with the numerical simulated results from the basic thermoelectric coupled equations is made, and excellent agreements are obtained.

Modelling the BiCMOS switching delay including radiation effects

The effect of ionising radiation on the BiCMOS switching response has been studied. The radiation-induced surface recombination current in the base of the bipolar transistor and the radiation-induced resistive leakage paths in the BiCMOS structure have been modelled as functions of the interface state density and the oxide trapped charge density. Radiation effects on the MOSFET and the bipolar transistor including leakage paths in the BiCMOS structure have been incorporated into the equivalent circuit of the proposed model. A semianalytical solution of the transient response of the BiCMOS gate is obtained including high injection and high current base push-out effects. The proposed model is compared with experimental data and with MEDICI simulations, and the agreement is good over a wide range of radiation levels. The BiNMOS gate has been demonstrated to be more radiation hard as compared to the BiPMOS gate.

Thermal Runaway Tolerance in Double-Heterojunction Bipolar Transistors

On the double-heterojunction bipolar transistor (DHBT) with a narrow band-gap base, collector current is strongly impeded at a high current level where the base-pushout effect occurs. This phenomenon was studied in conjunction with the thermal stability of transistors. The experimental comparison of Si/SiGe/Si-DHBT with a Si bipolar junction transistor (Si-BJT) confirmed that SiGe-DHBTs are more stable with regard to thermal runaway than Si-BJTs.

High-f/sub max/ AlGaAs/InGaAs and AlGaAs/GaAs HBT's with p/sup +//p regrown base contacts

The present paper describes a new approach to fabricating high performance HBT's with low base resistance. Their base contact resistance is reduced by using MOMBE selective growth in the extrinsic base region-a key process in the fabrication of high-f/sub max/ AlGaAs/InGaAs and AlGaAs/GaAs HBT's. A p/sup +//p regrown base structure, which consists of a 40-nm-thick graded InGaAs strained layer and a heavily C-doped regrown contact layer, is used for the AlGaAs/InGaAs HBT's to reduce both their base transit time and base resistance, while preventing aluminum oxide incorporation at the regrowth interface. An h/sub fe/ of 93, an f/sub T/ of 102 GHz, and an f/sub max/ of 224 GHz are achieved for a 1.6-/spl mu/m/spl times/4.6-/spl mu/m HBT, together with reduced base push-out effects and improved reliability. AlGaAs/GaAs HBT's with an 80-nm-thick uniform base layer that have high f/sub max/ values ranging from 140-216 GHz are also fabricated using the selective growth technique. These results confirm the high potential of the proposed HBT's, especially for microwave and millimeter-wave applications. >

Base pushout effect on collector signal delay and early voltage for heterojunction bipolar transistors

Base pushout effect on collector signal delay and early voltage for heterojunction bipolar transistors

Characteristics of impact-ionization current in the advanced self-aligned polysilicon-emitter bipolar transistor

Using an algorithm to calculate the base current increase due to local thermal effects, the authors show that one can accurately measure the impact ionization current over the full range of collector current. From the measured impact ionization ratio, it was possible to quantitatively describe the characteristics of the space-charge modulation and base push-out effect over a wide range of collector current. Computer simulation results support the measured data. It is also shown that one can use the measured impact ionization ratio to distinguish small collector concentration variations and thickness differences. The characterization was performed for self-aligned polysilicon-emitter transistors in an advanced BiCMOS technology. >

Low-temperature (77 K) BJT model with temperature dependences on the injected condition and base resistance

A low-temperature (77-K) bipolar transistor model based on physical analysis by considering the temperature dependences of the injection condition and base resistance modulation is described. A charge-based injection factor which describes the temperature dependence of the ideality factor n is introduced by taking into account the electron and hole concentration ratios at the edges of the emitter-base depletion layer. The temperature dependence of base resistance modulation is explained by using the temperature dependences of the conductivity modulation effect, the base pushout effect, and the emitter current-crowding effect. Calculations using the model are compared with measurements, revealing excellent agreement over a wide temperature range from 50 to 298 K. >

A 20-ps Si bipolar IC using advanced super self-aligned process technology with collector ion implantation

A super self-aligned process technology, SST-1B, which is an advanced version of the previously proposed SST-1A in high-speed Si bipolar LSIs is discussed. A selectively ion-implanted collector (SIC) process and bird's-beak-free isolation process are utilized. The SIC process is designed to improve shallow base-collector profiles in the intrinsic region. It reduces base width and intrinsic base resistance, and suppresses the base push-out effect (Kirk's effect) in high-current operations. The SIC profile is easily controlled by 150-200 keV phosphorous ion implantation at the base-collector junction. Using these processes, SST-1B has achieved a high cutoff frequency of 21.1 to 25.7 GHz and a fast switching delay of 20.5 ps/G for nonthreshold logic and 34.1 ps/G for emitter-coupled logic. SST-1B has potential applications to 50-ps/G logic LSIs and 10-GHz SSIs. Device simulation indicates that it is possible to achieve a cutoff frequency of 40-50 GHz in a future scaled-down Si bipolar transistor with a 40-nm base and graded collector. >

Modeling of bipolar transistor using integral charge-control model with application to third-order distortion studies

A compact bipolar transistor model [integral charge-control model (ICM)] has recently been developed that intrinsically includes many high-level effects (for example, conductivity modulation, base push-out effect, Early effect, and impact ionization). This paper presents a detailed characterization of a high-frequency silicon bipolar transistor using the ICM, with sufficient accuracy to allow calculation of intermodulation distortion. A set of electrical measurements for extracting ICM model parameters is described, and the method of extraction is discussed in detail. Finally, calculated values of second- and third-order distortion produced signals are compared with measured values and are found to be in good agreement, which demonstrates the accuracy of the ICM.