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A vertical IMOS transistor with a thin layer of strained SiGe in the impact ionization region near the drain is investigated by full-band Monte Carlo and hydrodynamic simulations for the first time. An anisotropic impact ionization model for strained SiGe based on the constant matrix approximation is applied in the Monte Carlo simulations. The results show that the reduced bandgap of the strained...
With Fermi's golden rule we have calculated the impact ionization (II) rates for strained SiGe. In our approach, the energy and the momentum are exactly conserved during the calculation of the six-dimensional integral in k-space over 4 conduction and 3 valence bands. The wave-vector space is discretized with a very fine grid with a spacing of up to 1/40 (2pi/a), where a is the lattice constant. II...
The noise behavior resulting from impact ionization (II) was investigated at room temperature for silicon-germanium (SiGe) heterojunction bipolar transistors with box Ge profile ("true" HBTs), featuring a maximum transit frequency of fT = 80 GHz. Noise parameters (NPs) were measured over a wide range of collector-emitter voltages. Modeling was performed using a generalized hydrodynamic (HD)...
In order to decrease bias voltages in IMOS devices we have proposed a new IMOS structure with Si/Si-Ge channel in this paper. In comparison with previously reported, single gate SOI IMOS and SGOI IMOS structures, this device can provide higher reduction in the source voltage as well as in threshold voltage. Moreover, the proposed structure provides considerable reduction in off-state current, while...
A new method for analyzing breakdown phenomena and differentiating between damage created by hot electrons and hot holes under impact ionization induced stress within SiGe HBTs is presented. Measurements demonstrate that electrons are more effective than holes for creating impact ionization induced damage under mixed-mode stress. Lucky electrons and lucky holes can be directly observed using this...
A unified electro-thermal safe operating area (SOA) expression is proposed in this paper to evaluate self heating, impact ionization, and hot carrier (HC) degradation effects simultaneously in a full range of bipolar transistor operation. This SOA is demonstrated by experiments for a SiGe hetero-junction bipolar transistor (HBT) fabricated on silicon on insulator (SOI) by extracting principle parameters...
We report the first demonstration of silicon-germanium (SiGe) impact-ionization MOS (I-MOS) transistors that feature a SiGe channel and a SiGe impact-ionization region. The lower bandgap of SiGe as compared to Si contributes to higher electron and hole impact-ionization rates, leading to avalanche breakdown at a much reduced source voltage and enhanced device performance. Both n-and p-channel I-MOS...
SiGe-heterojunction bipolar transistors (HBTs) still sustain their leading RF-application position due to their good noise and HF properties. They also offer a relatively high operating voltage, which is limited by BVCEO, the emitter collector breakdown voltage with open base. We show that BVCER, the avalanche breakdown with a resistor RB connected to the base, can be used to define reliable operating...
In modern RF BJTs and HBTs the collector is usually designed as selectively implanted collector (SIC). Therefore in the present work we investigate the influence of various SIC profiles on ft and f max with respect to BVCEO for four basic types of Si-based bipolar transistors: A SiGe HBT with a graded Ge content in the base, and second SiGe HBT having a much higher Ge content in the entire base, thus...
This paper reports a novel L-shaped impact-ionization MOS (LI-MOS) transistor technology that achieves subthreshold swing well below 60 mV/decade at room temperature. First, the LI-MOS transistor is CMOS process compatible, and requires little process modification for integration in a manufacturable process. Second, the LI-MOS structure employs raised source/drain (S/D) regions that enable controllability...
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