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Conventional techniques to characterize the carrier transport properties in high-electron-mobility transistors do not account for the effect of each individual unit process and device integration, and can be challenging to use for short-channel devices. To overcome this, we have developed a new technique that consists of measurement and analysis of the transconductance scaling behavior. The proposed ${g}_{m}$ modeling technique yielded the effective mobility, $\mu _{n\_{}{\textit {eff}}}$ , and saturation velocity, ${v}_{\textit {sat}}$ for fabricated InxGa $_{{1}-{x}}$ As Quantum-Well (QW) HEMTs, correlating the carrier transport properties to the device characteristics. This helps illuminate the physics of the carrier transport properties of HEMTs from the mobility relevant to the velocity saturation regimes.

We present a systematic study on the gate length ( ${L}_{{g}}\text {)}$ scaling behavior and the impact of the side-recess spacing ( ${L}_{\text {side}}\text {)}$ on dc and high-frequency characteristics of In0.8Ga0.2As quantum-well (QW) high-electron-mobility transistors (HEMTs) with ${L}_{{g}}$ from 10 $\mu $ m to 20 nm, for the purpose of understanding the scaling limit of maximum oscillation frequency ( ${f}_{\text {max}}\text {)}$ and thereby demonstrating terahertz devices. The fabricated In0.8Ga0.2As QW HEMTs with ${L}_{{g}} =20$ nm and ${L}_{\text {side}} =150$ nm exhibited values of drain-induced-barrier-lowering (DIBL) of 60 mV/V, current-gain cutoff frequency ( ${f}_{{T}}\text {)}$ of 0.75 THz, and ${f}_{\text {max}}$ of 1.1 THz, while the device with ${L}_{\text {side}} =50$ nm showed DIBL of 110 mV/V and ${f}_{{T}}$ / ${f}_{\text {max}}$ of 0.72/0.53 THz. It was central to strictly control short-channel effects (SCEs) from the perspective of DIBL to maximize the improvement of ${f}_{\text {max}}$ , as ${L}_{{g}}$ was scaled down deeply. In an effort to understand the ${L}_{{g}}$ scaling behavior of ${f}_{\text {max}}$ , we carried out the small-signal modeling for both types of devices and found that the increase of the intrinsic output conductance ( ${g}_{\text {oi}}\text {)}$ played a critical role in determining ${f}_{\text {max}}$ in short- ${L}_{{g}}$ HEMTs. On the contrary, the fabricated devices with ${L}_{\text {side}} =150$ nm exhibited a tight control of SCEs at ${L}_{{g}}$ of 20 nm. As a result, ${f}_{\text {max}}$ in those devices was boosted to 1.1 THz, and more importantly this high ${f}_{\text {max}}$ was maintained even as ${L}_{{g}}$ was scaled down to 20 nm. The results in this work represent the best balance of ${f}_{{T}}$ and ${f}_{\text {max}}$ in any transistor technology on any material system, displaying both ${f}_{{T}}$ and ${f}_{\text {max}}$ in excess of 700 GHz simultaneously.

Inactivation ofLactobacillussp. fromkimchiby high pressure carbon dioxide was investigated in a batch system. Inactivation rates increased with increasing pressure, temperature and exposure time, and with decreasing working volume ratio. Microbial reduction of 5 log cycles was observed within 200 min under a CO₂pressure of 70 kg/cm²at 30 °C. It was suggested that cell death resulted from the lowered intracellular pH due to penetration of CO₂, rather than physical rupture of cell walls due to the high pressure of CO₂. The experimental results suggested that high pressure CO₂treatment could be used as a potential nonthermal technique forkimchipreservation.Copyright 1997 Academic Press Limited

Baechu(Chinese cabbage) kimchiwas treated with high-pressure carbon dioxide at 70 kg/cm2for 24 h. The effect of this treatment on kimchifermentation during storage at 10°C was investigated in terms of pH value, titratable acidity, lactic acid bacterial count, and sensory properties. Kimchisamples treated with pressurized CO2had relatively a higher pH value, lower titratable acidity, and smaller lactic acid bacterial population than the untreated sample. A sensory evaluation showed that the sourness and overall acceptability of treated kimchiwere better than those of the control. The color, flavor and texture were not significantly affected by the treatment. The results indicate that high-pressure CO2treatment could be used as one of the applicable nonthermal processes for baechu kimchipreservation.