Velocity saturation

Cryoelectronics. Operation of CMOS devices at lower temperatures offers several advantages and some disadvantages (53). Operation at Hquid nitrogen temperatures (77 K) has been shown to double the performance of CMOS logic circuits (54). In part, this is the result of the increase in electron and hole mobilities with lower temperatures. The mobiHty decreases at high fields as carrier speeds approach saturation. Velocity saturation is more important for cryoelectronics because saturation velocities increase by only 25% at 77 K but saturation occurs at much lower fields. Although speedup can... 

A popular metric of the speed performance of a EET is, the maximum frequency of unity current gain (49). Eor short gate length devices operating at the saturated velocity this metric can be expressed as follows, where... 

The temperature sensitivity of the saturation velocity, Vsat, used in Eq. (4.5) to describe the effect of the lateral field, is additionally considered. The saturation velocity is moderately affected by temperature changes however, when the temperature largely deviates from Tnom. there is a strong effect on the saturation region characteristics of the transistor. The temperature dependence of the saturation velocity is taken into account using the temperature coefficient, AT, [BSIM 3.v3,129] ... 

The thermal conductivity of diamond at 300 K is higher than that of any other material, and its thermal expansion coefficient at 300 K is 0.8 x 10". lower than that of Invar (an Fe-Ni alloy). Diamond is a very widc-band gap semiconductor Eg = 5.5 eV), has a high breakdown voltage (I07V cm-1), and its saturation velocity of 2.7 x I01 cm s-1 is considerably greater than that of silicon, gallium arsenide, or indium phosphide. 

The Johnson figure of merit (JFM) is used to compare materials for power microwave applications. Larger values indicate superior performance in microwave power applications. The higher the value, the higher will be the power capability. This figure of merit is the product of the breakdown voltage (Vb) and the electron saturation velocity (Ljat). 

Similar to the concentration sharpening front (shock), the satnration shock front discussed previously may not always form. A shock front may form if the saturation velocities upstream are greater than those downstream. This is true for most oil/water fractional flow curves between certain limits of saturation, depending on the curvature of the fractional flow curve (Pope, 1980). If we cannot draw a tangent to the fractional flow curve, then a good flood front will not form (Craig, 1971). 

TABLE 2.10 Saturated Velocity and Critical Field for Si at Room Temperature... 

Saturated velocities Maximum carrier velocity induced by electric field (due to onset of inelastic scattering). 

R. A. Alberty and W. H. Pierce, J. Am. Chem. Soc. 79, 1526 (1957)], where K+ and K are the saturation velocities for the forward and reverse reactions, respectively. Compute Gobs and as many of the four rate constants as the data permit. 

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