Phase change memory (PCM) cells with T-shaped structure using tungsten heater were fabricated and the cell characteristics concerning the programing pulse width were also investigated in this work. The numerical modeling shows the thermal nonuniformity over the active region due to the considerable thermal sink of tungsten heater results in the amorphous-phase residues and the incomplete set programing. The experimental results reveal the existence of residual amorphous phase and indicate that the incomplete set programing is the dominant factor to degrade the PCM cell performances, such as the sensing margin and the endurance. The strategies to eliminate the incomplete set programing are the optimization in programing pulse width and the replacement of the tungsten heater with higher resistivity metal such as TiAlN.

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A novel phase-change memory cell with a doubleconfinement structure was proposed and fabricated in this work. By having an additional bottom Ge 2 Sb 2 Te 5 layer under the electrically confined active region, the heat loss can be effectively prevented. The temperature uniformity over the active region significantly improves and so does the thermal efficiency. Therefore, a low I RESET of about 0.3 mA and a reset power can be achieved. For the SET performance, a pulsewidth as low as 200 ns can be used without compromising the R SET .

This study examined the effects of three cumulative c-ray irradiation doses on AlGaN/GaN epilayer material and on high electron mobility transistor (HEMT) devices. After a cumulative c-ray dose of 16 kGy, the Hall mobility increased from 1800 cm 2 /V s to 2100 cm 2 /V s, as determined through Hall measurement. Atomic force microscopy indicated an improvement in surface roughness but no change in the surface potential ; s ð Þ. The HEMT device exhibited improvement in the drain current, with a subtle decreasing tendency in the leakage current. At high doses of c-ray irradiation, the trends in the material and device parameters saturated. Moreover, the metal-semiconductor interface degraded, as confirmed through scanning electron microscopy image analysis.

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