Yao Ruohe

Photovoltage analysis of a heterojunction solar cell

According to the p—n junction model of Shockley, the relationship between the equilibrium carrier concentrations of n-type and p-type semiconductors on the edges of the depletion region of a p—n junction solar cell is analysed. The calculation results show that the photovoltage can exceed the built-in voltage for a special kind of heterojunction solar cell. When the photovoltage exceeds the built-in voltage under illumination, the dark current and the photocurrent are impeded by the peak of voltage barrier at the interface and the expression of the total I—V characteristic is given.

Positive gate-bias temperature instability of ZnO thin-film transistor

The positive gate-bias temperature instability of a radio frequency (RF) sputtered ZnO thin-film transistor (ZnO TFT) is investigated. Under positive gate-bias stress, the saturation drain current and OFF-state current decrease, and the threshold voltage shifts toward the positive direction. The stress amplitude and stress temperature are considered as important factors in threshold-voltage instability, and the time dependences of threshold voltage shift under various bias temperature stress conditions could be described by a stretched-exponential equation. Based on the analysis of hysteresis behaviors in current—voltage and capacitance—voltage characteristics before and after the gate-bias stress, it can be clarified that the threshold-voltage shift is predominantly attributed to the trapping of negative charge carriers in the defect states located at the gate—dielectric/channel interface.

High-photosensitivity polymer thin-film transistors based on poly(3-hexylthiophene)

Polymer thin-film transistors (PTFTs) based on poly(3-hexylthiophene) are fabricated by the spin-coating process, and their photo-sensing characteristics are investigated under steady-state visible-light illumination. The photosensitivity of the device is strongly modulated by gate voltage under various illuminations. When the device is in the subthreshold operating mode, a significant increase in its drain current is observed with a maximum photosensitivity of 1.7 10 3 at an illumination intensity of 1200 lx, and even with a relatively high photosensitivity of 611 at a low illumination intensity of 100 lx. However, when the device is in the on-state operating mode, the photosensitivity is very low: only 1.88 at an illumination intensity of 1200 lx for a gate voltage of 20 V and a drain voltage of 20 V. The results indicate that the devices could be used as photo-detectors or sensors in the range of visible light. The modulation mechanism of the photosensitivity in the PTFT is discussed in detail.

Fabrication of a ZnO:Al/Amorphous-FeSi2 Heterojunction at Room Temperature

A prototype ZnO:Al/amorphous-FeSi2 heterojunction was successfully prepared on a glass substrate by magnetron sputtering at room temperature. The structural and electrical properties of as-deposited FeSi2 thin films were investigated using x-ray diffraction, Raman scattering, resistivity, and carrier lifetime measurement. The FeSi2 thin film showed an amorphous phase with resistivity of 9.685 ??cm and carrier lifetime of 9.5 ?s. The prototype ZnO:Al/amorphous-FeSi2 heterojunction exhibited a rectifying property of the diode from the dark current-voltage characteristic. This propert was evaluated using the shunt resistance and diode ideal factor. The experimental results suggest that the amorphous-FeSi2 thin film has promising applications in heterojunction devices with low thermal budget and low product cost.

Building-in Reliability for VLSI

Building-in reliability (BIR) was introduced in the early of 1990s. It is a methodology to manufacture highly reliable IC by minimizing and eliminating the sources of product unreliability in the beginning of a new product process. The characteristic of integrated reliability about BIR diffuses the responsibility for reliability into the whole team, including not only the process/ reliability/ characterization engineers, but also the applied research engineers and the customers who use integrated circuits. Its well known that the quality and reliability are defined by the customer, not by the manufacturers. So the customers role in BIR is very important, especially the responsibilities of establishing good communications with the manufacturer and returning all failures to the manufacturer. The quality function deployment (QFD) and qualified manufacturers list (QML) can help the customer take his responsibilities. In addition, nowadays little progress has been made in charactering the reliability of the future high reliability of VLSI after using the BIR approach. Small-sample statistical theory, especially for support vector machines (SVM) will be attempted to assess the reliability of VLSI.

The Influence of the Negative Radial Electric Field on the Orbit of Banana Particles in Tokamak

This paper explores the patterns of influence of the negative radial electric field on the drift displacement and trajectory of charged particles, for it is essential for further investigation into the transitional mechanism of L-H Mode. In the light of superposition between the poloidal velocity of charged particles and the E × B drift caused by the negative radial electric field, the paper offers a theoretical analysis and value simulations. Under the action of different radial electric fields, results have been obtained in regard to changes in the velocity of charged particles (mainly ions), patterns of changes in drift displacement, regional change of banana particles, and features of transition and change between trajectories of transiting particles and banana particles.