Transport characteristics of N-ZnS are calculated by solving the Boltzmann transport equation using a variational method (including all major scattering mechanisms and screening). The dependence of electron mobility on carrier concentration, for a range of compensation ratio and ionized impurity concentration, are given at both 300 and 77 K. This provides a rapid means for determining material quality. Mobility limits of 230 cm2/V s (n∼1019 cm−3) and over 3000 cm2/V s (n<1014 cm−3) are calculated at 300 and 77 K, respectively. The temperature dependence of the mobility is calculated and agrees favorably with experimental data.

In recent years, Ta 2 O 5 has been researched due to its high dielectric constant. It has gained attention for its application on storage capacitors for dynamic random access memory (DRAM), gate oxide 1 and lightly doped drain spacer 2 for future deep submicrometer metal oxide semiconductor field effect transistors (MOSFETs). In the past, efforts have been made to deposit Ta 2 O 5 on polysilicon bottom electrodes using different deposition systems and annealing processes. [3][4][5][6][7][8][9][10][11][12][13] However, poor electrical properties of Ta 2 O 5 deposited by low pressure chemical vapor deposition (LPCVD) were often obtained when carbon-based Ta(OC 2 H 5 ) 5 was used as the precursor in the mass production processes. 4-8 Therefore, many oxygen annealing processes such as dry-O 2 rapid thermal annealing (RTA), 8 O 2 -plasma annealing, 4-6 two-step annealing, 3 UV-O 3 annealing, 3 and N 2 O RTA 9 or furnace N 2 O annealing 10 were studied extensively. Although the leakage current density was well suppressed by these annealing processes mentioned above, it also accompanied a decay in dielectric constant. [8][9][10] This was due to the formation of a very thin SiO 2 layer about 2 nm between Ta 2 O 5 and the polysilicon interface after a high temperature annealing process. The capacitance was decreased due to the additional low dielectric constant SiO 2 layer. 9,10 This problem could be lessened by using refractory metal electrode such as tungsten. However, the leakage current level of 1 ϫ 10 Ϫ7 A/cm 2 at 1 V was at least one order of magnitude larger than that of Ta 2 O 5 deposited on polysilicon by LPCVD. 4 In this work, high quality thin Ta 2 O 5 films (14 nm) are deposited by PECVD on tungsten bottom electrode using a pentaethoxytantalum Ta(OC 2 H 5 ) 5 as the precursor. Material properties are investigated by X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS). The electrical measurements, including current-voltage (I-V) and capacitance-voltage (C-V) characteristics are performed on Au/Ta 2 O 5 /W/p-Si devices. The current conduction mechanism of Ta 2 O 5 films is investigated. A comparison is also made between Ta 2 O 5 films deposited by PECVD and LPCVD. Experimental (100) p-type silicon wafers (8.5-11.5 ⍀ cm) were used as the starting material. The silicon wafers were first deposited with 500 nm of chemical vapor deposited tungsten using WF 6 and SiH 4 as reactants. The Ta 2 O 5 film was then deposited in an O 2 ambiant at 400ЊC. Ta 2 O 5 films were deposited on separate silicon wafers simultaneously to measure the refractive index and the film thickness. The Ta(OC 2 H 5 ) 5 was vaporized in the source tank in the temperature range of 140 to 170ЊC and was carried to the deposition chamber using nitrogen as the carrier gas. The precursor was then transferred to the reactor through a gas heating line. The gas heating line was maintained at a higher temperature of 160 to 190ЊC to prevent recondensation of Ta(OC 2 H 5 ) 5 . The chamber was maintained at 0.3 to 0.4 Torr during deposition. T...

Flexible top-gate amorphous InGaZnO TFTs array on a colorless polyimide substrate for AMOLED applications was successfully fabricated at 200 o C for the first time. The light transmittance of polyimide substrate is 90%. The maximum field-effect mobility is 10.6 cm 2 /V-s, subthreshold swing is 0.3 V/decade, and the on/off current ratio is 10 8 .

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