Back-to-back Schottky diode adopted for the measurement of GaN films and its Schottky contacts

A new measurement method for GaN films and their Schottky contacts is reported in this paper. Instead of the fabrication of Ohmic contacts, this measurement is based on a special back-to-back Schottky diode that has a rectifying character. A mathematical model indicates that the electronic parameters of the materials can be deduced from the device's I-V data. In the experiment of an unintentionally doped n-type GaN layer with a residual carrier density 7 x 10(16) cm(-3), the analysis by the new method gives the layer's sheet resistance rho(s) = 497 Omega, the electron mobility mu(n) =, 613 cm(2) V-1 s(-1) and the ideality factor of the Ni/Au-GaN Schottky contacts n = 2.5, which are close to the data obtained by the traditional measurements: rho(s) = 505 Omega, mu(n) = 585 cm(2) V-1 s(-1) and n = 3.0. The method reported can be adopted not only for GaN films but also for other semiconductor materials, especially in the cases where Ohmic contacts of high quality are hard to make or their fabricating process affects the film's character.

不同森林管理预案下友好林业局森林景观的动态变化

Knowledge about cumulative effects of forest management alternatives on forest landscape is required to make forest management decision. In this paper,a spatially explicit landscape model,LANDIS,was applied to simulate forest landscape changes in 200 years under four management alternatives (no cutting,clearcutting,selective cutting I and II) in Youhao Forestry Bureau located in Small Khingan Mountains. APACK was used to calculate distribution area of the representative species and species age cohort for six species. The results showed:1) timber harvest decreased area percentage of representative conifer species,Pinus koraiensis,Picea koraiensis and Picea jezoensis,Larix gmelinii to some extent compared to no cutting. The most influencing cutting mode for the area percentage of Tilia amurensis and Quercus mongolica was selective cutting II,followed by selective cutting I and clearcutting. To the contrast,the change of area percentage of Betula phatyphylla was contrary to the management alternatives; 2) As to species age cohort composition,timber harvest significantly changed age structure,that is,it decreased over-matured age cohort of representative species,and increased seedling and middle-age cohort (B. phatyphylla was not included,because its area percentage of over-mature age cohort was the highest under clearcutting than other three scenarios).

性别、效价及媒体对选择冲突问题解决的影响

Choice conflict is a critical issue in decision making. This study adopted stock transaction as the task to explore the relation between share price level and conflict intensity that the subjects experienced in decision making, and the effect of price level on individual and group choice conflict resolution. The strategy people used to solve choice conflict and gender difference were also examined. Modes of interaction (face to face and through audio media) in group decision making were also studied. The main results are as follows: 1. In individual decision-marking, there is a significant gender effect on decision time. Female subjects will spent more time on the task than male subjects. 2. When making a choice decision, the individual experienced stronger conflict for price shares than for low price shares. The stronger the conflict level they feel, the more difficult to make the choice decision. 3. Four strategies were used to finish the task. Male subjects used simple strategies while female subjects used more complex strategies. 4. In group decision-making, share price level had a significant effect on selection time. People used longer selection time for low price shares than for high price shares. No significant interaction was found between share price level and Modes of interaction. 5. Modes of interaction had significant effect on satisfaction coherence of the group. Under face-to-face condition, people within one group had greater satisfaction coherence. 6. Media had no significant effect on people's perception during the experiment. Satisfaction for cooperation, successful communication and good cooperation were correlated. Self satisfaction and satisfaction of the partners others were also correlated with the satisfaction of the whole task.