An experimental study about the influence of well thickness on the electroluminescence of InGaN/GaN multiple quantum wells

The influence of well thickness on the electroluminescence (EL) of InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition is investigated. It is found that the peak wavelength of EL increases with the increase of well thickness when the latter is located in the range of 3.0-5.1 nm. The redshift is mainly attributed to the quantum confined Stark effect (QCSE). As a contrast, it is found that the EL intensity of InGaN/GaN MQWs increases with the increase of well thickness in spite of QCSE. The result of X-ray diffraction demonstrates that the interface become smoother with the increase of well thickness and suggests that the reduced interface roughness can be an important factor leading to the increase of EL intensity of InGaN/GaN MQWs. (C) 2009 Elsevier B.V. All rights reserved.

Theoretical analysis about the influence of channel layer thickness on the 2D electron gas and its distribution in InP-based high-electron-mobility transistors

The principle of high-electron-mobility transistor (HEMT) and the property of two-dimensional electron gas (2DEG) have been analyzed theoretically. The concentration and distribution of 2DEG in various channel layers are calculated by numerical method. Variation of 2DEG concentration in different subband of the quantum well is discussed in detail. Calculated results show that sheet electron concentration of 2DEG in the channel is affected slightly by the thickness of the channel. But the proportion of electrons inhabited in different subbands can be affected by the thickness of the channel. When the size of channel lies between 20-25 nm, the number of electrons occupying the second subband reaches the maximum. This result can be used in parameter design of materials and devices.

Study on Mechanics Parameters of Unloaded Rock Mass about the Underground Powerhouse of Jin-ping Hydroelectric Station

After the excavation of Jinping underground cavern, a strong expansion appears along the unloading direction of the rock mass, mainly in the type of tensile rupture, accompanied by shear destruction, unloading resulted in significant deterioration of mechanical properties of rock. Based on the in-site investigation of rock mass structure, via analyzing the acoustic testing data, we identify the unloading range of the side walls and the division of rock types, and carry out with the solution of rock mechanical parameters about different unloading zone, providing geological foundation for the supporting design of the following design of the side walls, at the same time, providing reference for the selection of mechanical parameters of other underground excavation engineering with similar geological conditions.