Carrier relaxation and thermal activation of localized excitons in self-organized InAs multilayers grown on GaAs substrates

We have investigated the temperature dependence of photoluminescence (PL) properties of a number of self-organized InAs/GaAs heterostructures with InAs layer thickness ranging from 0.5 to 3 ML. The temperature dependence of InAs exciton emission and linewidth was found to display a significant difference when the InAs layer thickness is smaller or larger than the critical thickness around 1.7 ML. The fast redshift of PL energy and an anomalous decrease of linewidth with increasing temperature were observed and attributed to the efficient relaxation process of carriers in multilayer samples, resulting from the spread and penetration of the carrier wave functions in coupled InAs quantum dots. The measured thermal activation energies of different samples demonstrated that the InAs wetting layer may act as a barrier for the thermionic emission of carriers in high-quality InAs multilayers, while in InAs monolayers and submonolayers the carriers are required to overcome the GaAs barrier to escape thermally from the localized states.

Effect of Carrier Gas Flux on ZnO Nanorod Arrays Grown by MOCVD

ZnO nanorod arrays with different morphologies were grown by metalorganic chemical vapor deposition （MOCVD）. The diameters of nanorods range from 150 nm to 20 nm through changing the carrier gas flux during the growth process. Measurements such as scanning electron microscope （SEM）, X-ray diffraction （XRD）, Raman scattering and photoluminescence （pL） spectrum were employed to analyze the differences of these nanorods. It was found that when both carrier gas flux of Zn and O reactant are 1 SLM, we can obtain the best vertically aligned and uniform nanorods. Furthermore, the PL spectrum reveals a blueshift of UV emission peak, which may be assigned to the increase of surface effect.

Carrier Depth Profile of Si/SiGe/Si n-p-n HBTStructural Materials Characterized by Electrochemical Capacitance- Voltage Method

于2010-11-23批量导入

Effect of carrier relaxation and emission on photoluminescence of InAs quantum dots

　

Behavior of Pentacene Initial Nucleation on Various Dielectrics and Its Effect on Carrier Transport in Organic Field-Effect Transistor

The influence of dielectric surface energy on the initial nucleation and the growth of pentacene films as well as the electrical properties of the pentacene-based field-effect transistors are investigated. We have examined a range of organic and inorganic dielectrics with different surface energies, such as polycarbonate/SiO2, polystyrene/SiO2, and PMMA/SiO2 bi-layered dielectrics and also the bare SiO2 dielectric. Atomic force microscopy measurements of sub-monolayer and thick pentacene films indicated that the growth of pentacene film was in Stranski-Kranstanow growth mode on all the dielectrics. However, the initial nucleation density and the size of the first-layered pentacene islands deposited on different dielectrics are drastically influenced by the dielectric surface energy. With the increasing of the surface energy, the nucleation density increased and thus the average size of pentacene islands for the first mono-layer deposition decreased. The performance of fabricated pentacene-based thin film transistors was found to be highly related to nucleation density and the island size of deposited Pentacene film, and it had no relationship to the final particle size of the thick pentacene film. The field effect mobility of the thin film transistor could be achieved as high as 1.38 cm(2)/Vs with on/off ratio over 3 x 10(7) on the PS/SiO2 where the lowest surface energy existed among all the dielectrics. For comparison, the values of mobility and on/off ratio were 0.42 cm(2)/Vs and 1 x 10(6) for thin film transistor deposited directly on bare SiO2 having the highest surface energy.