Bipolar devices device performance

A Bhalla, TP Chow. Bipolar power device performance dependence on materials, lifetime, and device ratings. International Symposium on Power Semiconductor Devices and ICs, 1994, p 287. M Bhatnagar, H Nakanishi, S Bothra, PM McLarty, BJ Baliga. Edge terminations for SiC high voltage Schottky rectifiers. International Symposium on Power Semiconductor Devices and ICs, 1993, p 89. 

Certain features in the PR spectra at 300 K from GaAs/Gai j,jAlj heterojunction bipolar transistor structures have been correlated with actual device performance thus PR can be used as an effective screening tool. From the observed FK oscillations it has been possible to evaluate the built-in dc electric fields in the Gai j jAlj emitter, as well as in the n—GaAs collector region. The behavior... 

In real device structures like heterojunction bipolar transistors, certain features in the PR spectrum can be correlated with actual device performance. Thus PR has been employed as an effective contacdess screening technique to eliminate structures that have imwanted properties. 

Both CMOS and bipolar devices encapsulated with the new transfer molding compositions performed well under thermal cycling between -65°C and + 150°C and also under accelerated life testing at 145°C, 85% RH and 18V bias. Further optimization of this type of molding composition is expected to improve its performance as a protective material for integrated circuitry. 

The properties of the host material generally determine device performance. Depending on the charge-transporting properties of the host, recombination can occur at the interface with the blocking layer or in the bulk of the EML. A bipolar host can promote bulk recombination, but can also lead to a situation where the recombination occurs at both the EML HTL and EML IETL interfaces, in particular, when the electric field and the mobility of charge carriers in the EML are high. ... 

Abstract We review the methods used to simulate the optoelectronic response of organic solar cells and focus on the application of one-dimensional drift-diffusion simulations. We discuss how the important physical processes are treated and review some of the experiments necessary to determine the input parameters for device simulations. To illustrate the usefulness of drift-diffusion simulations, we discuss several case studies, addressing the influence of charged defects on transport in bipolar and unipolar devices, the influence of defects on recombination, device performance and ideality factors. To illustrate frequency domain simulations, we show how to determine the validity range of Mott-Schottky plots for thin devices. Finally, we discuss an example where optical simulations are used to calculate the parasitic absorption in contact layers. 

Materials issues in bipolar junction transistors have driven massive materials research programs. Through these, the current bipolar junction transistor performances have been achieved. Much of the discussion of circuit technologies has focused on smaller and smaller transistors. The above examples and discussion hopefully convey that advances can be achieved by other means as well. This is useful as at some point the continuing reduction in device scale must end. 

Aqueous, alkaline fuel cells, as used by NASA for supplemental power in spacecraft, are intolerant to C02 in the oxidant. The strongly alkaline electrolyte acts as an efficient scrubber for any C02, even down to the ppm level, but the resultant carbonate alters the performance unacceptably. This behavior was recognized as early as the mid 1960 s as a way to control space cabin C02 levels and recover and recycle the chemically bound oxygen. While these devices had been built and operated at bench scale before 1970, the first comprehensive analysis of their electrochemistry was put forth in a series of papers in 1974 [27]. The system comprises a bipolar array of fuel cells through whose cathode chamber COz-containing air is passed. The electrolyte, aqueous Cs2C03, is immobilized in a thin (0.25 0.75 mm) membrane. The electrodes are nickel-based fuel cell electrodes, designed to be hydrophobic with PTFE. 

See also CMOS image sensors bipolar transistors with, 22 249 improving performance of, 22 257 logic circuits with, 22 251-253 Moore s law and device scaling and,... 

Due to the new developments [5] in fuel cell technology—the manufacture of carbon supported platinum catalysts and the use of the Nafion membrane—the cost of bipolar electrolyzers has been reduced a lot, and therefore almost all commercial devices are of this type. In this case, stainless steel or nickel cathodes are used together with nickel anodes in 25%-35% of potassium hydroxide at temperatures between 65°C and 90°C. The hydrogen current density reaches 100-300 mA/cm2 at cell potentials of 1.9-2.2 V, denoting a faradaic efficiency of 80% (losses in peripheries). Usually, a pressurized cell is employed to increase their performance and to reduce the size of the bubbles, thus lowering the overpotential associated with the process. This can be done with appropriate membranes and insulators and by using temperatures near 100°C. 

Mobile telephones incorporate multilayer III-V epitaxial heterojunction bipolar transistor wafers such as that illustrated in Figure 27.12. The p-n junctions on either side of the base layer are a crucial feature of semiconductor devices, and in the wafer shown in Figure 27.12 (and in other similar wafers), the p-type base layer must be highly doped to provide high-frequency performance. Choice of dopant is critical, e.g. use of a Zn dopant (see below) results in its diffusion into the emitting n-type layers. This problem has been overcome by doping with C which exhibits a low diffusion coefficient C-doped wafers have been used commercially since the early 1990s. 

SiC bipolar transistors have been fabricated and measured. Improved performance is to be expected in heterojunction devices with a wider bandgap emitter. A feasibility study is underway to make a non-volatile random access memory in SiC. 

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