Optimization of InGaAs Quantum Dots for Optoelectronic Applications

Self-assembled In_0.35Ga_0.65As/GaAs quantum dots with low indium content are grown under different growth temperature and investigated using contact atomic force microscopy(AFM). In order to obtain high density and high uniformityu of quantum dots, optimized conditions are concluded for MBE growth. Optimized growth condi-tions also compared with these of InAs/GaAs quantum dots. This will be very useful for InGaAs/GaAs QDs opto-electronic applications, such as quantum dots lasers and quantum dots infrared photodetectors.

Quasi-Thermodynamic Model of MOVPE of InAlN

国家自然科学基金

Quasi-Thermodynamic Model for MOVPE of AlGaN

国家863计划,国家自然科学基金

Optimization of InGaAs quantum dots for optoelectronic applications

Quantum dot infrared photodetectors (QDIP) are in the center of research interest nowadays. However the real QDIP is inferior to those predicted in theory, in which the dot density is much higher than those reported. Through optimizing the growth conditions, we realized the control of high-density quantum dot growth. This will be very useful for future QDIP development.

Thermodynamic analysis of GaSb-GaCl3 vapor phase epitaxy

A thermodynamic model for the GaSb-GaCl3 system in a closed quartz ampoule was proposed. The species in the gas phase are GaCl, GaCl3, Sb-4, Sb-2. The partial pressures of these species and total pressure in the ampoule have been calculated. The calculated results indicate that the equilibrium partial pressures of GaCl, GaCl3, Sb4, Sb2 and the total pressure in the ampoule have strong dependence on temperature, free volume inside the closed ampoule and amount of transport agent GaCl3. The total pressure will give strong influence not only on the flow pattern in the ampoule, but also on the uniformity of the epilayer.

Using photoluminescence as optimization criterion to achieve high-quality InGaAs/AlGaAs pHEMT structure

The single delta -doped InGaAs/AlGaAs pseudomorphic HEMT structure materials were grown by molecular beam epitaxy. The photoluminescence spectra of the materials were studied. There are two peaks in the photoluminescence spectra of the materials, corresponding to two sub energy levels of InGaAs quantum well. The ratio of the two peak's intensity was used as criterion to optimize the layer structures of the materials. The material with optimized layer ;tructures exhibits the 77 It mobility and two-dimensional electron gas density of 16 500 cm(2)/Vs and 2.58 x 10(12) cm(-2) respectively, and the 300 K mobility and two-dimensional electron gas density of 6800 cm(2)/Vs and 2.55 x 10(12) cm(-2) respectively. The pseudomorphic HEMT devices with gate length of 0.2 mum were fabricated using this material. The maximum transconductance of 650 mS/mm and the cut-off frequency of 81 GHz were achieved. (C) 2001 Elsevier Science B.V. All rights reserved.

Design and optimization of highly nonlinear low-dispersion crystal fiber with high birefringence for four-wave mixing

We have proposed a novel type of photonic crystal fiber (PCF) with low dispersion and high nonlinearity for four-wave mixing. This type of fiber is composed of a solid silica core and a cladding with a squeezed hexagonal lattice elliptical airhole along the fiber length. Its dispersion and nonlinearity coefficient are investigated simultaneously by using the full vectorial finite element method. Numerical results show that the proposed highly nonlinear low-dispersion fiber has a total dispersion as low as +/- 2.5 ps nm(-1) km(-1) over an ultrabroad wavelength range from 1.43 to 1.8 mu m, and the corresponding nonlinearity coefficient and birefringence are about 150 W-1 km(-1) and 2.5 x 10(-3) at 1.55 mu m, respectively. The proposed PCF with low ultraflattened dispersion, high nonlinearity, and high birefringence can have important application in four-wave mixing. (C) 2010 Optical Society of America

Thermodynamic theory of the Tolman's length

There still exists controversy on the sign and magnitude of the Tolman's length and the Tolman's gap. Further experimental, computational and theoretical investigations on them are needed to solve this problem. In 2006, Blokhuis and Kuipers obtained a rigorous relationship between the Tolman's length and other thermodynamic quantities for the single-component liquid-vapour system. In the present paper, we derive two general relationships between the Tolman's length and other thermodynamic quantities for the single-component liquid vapour system. The relationship derived by Blokhuis and Kuipers and an earlier result turn out to be two special cases of our results.

Optimization of evanescent wave imaging for the visualization of protein adsorption layers

We have optimized the settings of evanescent wave imaging for the visualization of a protein adsorption layer. The enhancement of the evanescent wave at the interface brought by the incident angle, the polarized state of light beam as well as a gold layer is considered. In order to improve the image contrast of a protein monolayer in experiments, we have optimized three factors-the incident angle, the polarization of light beam, and the thickness of an introduced thin gold layer with a theoretical simulation.

CFD analysis of thermodynamic cycles in a pulse tube refrigerator

The objectives of this paper are to study the thermodynamic cycles in an inertance tube pulse tube refrigerator (ITPTR) by means of CFD method The simulation results show that gas parcels working in different parts of ITPTR undergo different thermodynamic cycles The net effects of those thermodynamic cycles are pumping heat from the low temperature part to the high temperature part of the system The simulation results also show that under different frequencies of piston movement the gas parcels working in the same part of the system will undergo the same type of thermodynamic cycles The simulated thermal cycles are compared with those thermodynamic analysis results from a reference Comparisons show that both CFD simulations and theoretical analysis predict the same type of thermal cycles at the same location However only CFD simulation can give the quantitative results while the thermodynamic analysis is still remaining in quality (C) 2010 Elsevier Ltd All rights reserved