A systematic study has been performed to investigate the flow and thermal patterns of vertical rotating Thomas Swan MOCVD reactor at low pressure, using 2-D dynamic modeling. By varying and calculating the several important process parameters of the reactor, the optimized conditions of the uniform distributions of velocity and temperature profiles in steady state have been obtained. Then, time-dependent models with the step response perturbation of the total gas rate can help identify the visual transient behavior inside the reactor and analyze the mechanism of delay time, relaxation oscillation and pulsative oscillation. These results are beneficial to the process parameter optimization and geometrical configuration design of the MOCVD reactor. heteroepitaxy, MOCVD reactor, transport process, flow fields and thermal Citation: Zhong S Q, Ren X M, Huang Y Q, et al. Numerical studies on flow and thermal fields in MOCVD reactor. The metalorganic chemical vapor deposition (MOCVD) equipment was invented by Manasevit et al. [1] in 1968. Nowadays, this equipment has been extensively used for the large-scale production of microelectronic and optoelectronic devices with compound semiconductor materials in highspeed optical communication, 3G mobile communication, broad band satellite communication, high-efficiency solar cell and so on [2−6].During MOCVD growth, a mixture of precursor vapors containing the source elements to be incorporated in the very thin film is diluted in a carrier gas and flows over a heated substrate, resulting in epitaxial growth of a very thin solid film. To grow heterojunction semiconductor materials and devices, precursors are turned on and off periodically into a steady flow of the carrier gas. This periodic switching creates many transient processes in the reactant supply to the substrate. To achieve abrupt interfaces during heterostructure growth, the component transients should ideally be shorter than the time needed to grow one atomic layer. Especially in recent years, the transient problem was been getting more and more important for the fabrication of quantum dots (QDs), quantum wires (QWs) and multiquantum wells (MQWs) to grow the advanced nanometer scale materials and devices. So, we not only focus on the time required for the entire reactor to reach a new steady state, but also are interested in the duration of transients above the substrate. Solving this problem will provide an efficient growth of the semiconductor materials with desirable physical properties that are often inaccessible by conventional approach.Since the 1980s, the study on transport phenomena in MOCVD reactor has become one of the most important and extensive subjects. The researchers have utilized hydraulic experiments, optical measurements [7−9] and advanced computational fluid dynamics (CFD) [10−21] to study the extremely complicated mass transportation in the reactor and lots of progress has been achieved. However, all previous work concentrates on the side of steady state flow, and particularly emphasizes the inno...

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The dynamics of two qubits ultra-strongly coupled with a quantum oscillator is investigated by the adiabatic approximation method. The evolution formula of the initial four Bell states are studied under the control mechanism of the coherent state of the quantum oscillator. The influential parameters for the preservation of the entanglement are the four parameters: the average number of the coherent state, the ultra-strong coupling strength, the ratio of two frequencies of qubit and oscillator, and the inter-interaction coupling of the two qubits. The novel results show that the appropriate choice of these parameters can enable this mechanism to be utilized to preserve the entanglement of the two qubits, which is initially in the state |I0 of the four Bell states. We give two different schemes to choose the respective parameters to maintain the entangled state |I0 almost unchanged. The results will be helpful for the quantum information process.

The entanglement of two qubits is investigated in the range of their ultra-strongly coupling with a quantum oscillator. The two qubits are initially in four Bell states and they are under the control mechanism of the coherent state of the quantum oscillator. There are four parameters: the average number of the coherent state, the ultra-strong coupling strength, the ratio of two frequencies of qubit and oscillator, and the inter-interaction coupling of the two qubits in the mechanism, and they all are influential parameters on the entanglement of the two qubits. One Bell state |0 is easyily kept and is trivial case. The novel results show that there is one state |I0 among the other three Bell states which the entanglement of the two qubits could be almost completely preserved. The possibility is made into reality by the appropriate choice of the four influential parameters. We give two different schemes to choose the respective parameters to maintain the entanglment of |I0 almost undiminished. The results will be useful for the quantum information process.