Study on the perfection of in situ P-injection synthesis LEC-InP single crystals

Undoped, S-doped and Fe-doped InP crystals with diameter up to 4-inch have been pulled in drop 10 0 drop -direction under P-rich condition by a rapid P-injection in situ synthesis liquid encapsulated Czochralski (LEC) method. High speed photoluminescence mapping, etch-pit density (EPD) mapping and scanning electron microscopy have been used to characterize the samples of the single crystal ingots. Dislocations and electrical homogeneity of these samples are investigated and compared. By controlling the thermal field and the solid-liquid interface shape, 4-inch low-EPD InP single crystals have been successfully grown by the rapid P-injection synthesis LEC method. The EPD across the wafer of the ingots is less than 5 x 10(4) cm(-2). Cluster defects with a pore center are observed in the P-rich LEC grown InP ingots. These defects are distributed irregularly on a wafer and are surrounded by a high concentration of dislocations. The uniformity of the PL intensity across the wafer is influenced by these defects. (C) 2004 Elsevier B.V. All rights reserved.

Influence of crystal perfection on the reverse leakage current of the SiGe Si p-n heterojunction diodes

Double-crystal X-ray diffraction and I-V characterization have been carried out on the GSMBE grown SiGe/Si p-n heterojunction materials. Results show that the SiGe alloys crystalline quality and the misfit dislocations are critical influences on the reverse leakage current. The crystal perfection and/or the degree of metastability of the Sice alloys have been estimated in terms of the model proposed by Tsao with the experimental results. High-quality p-n heterojunction diodes can be obtained by optimizing the SiGe alloy structures, which limit the alloys in the metastable states. (C) 1999 Elsevier Science B.V. All rights reserved.

Influence of crystal perfection on the reverse leakage current of the SiGe Si p-n heterojunction diodes

Double-crystal X-ray diffraction and I-V characterization have been carried out on the GSMBE grown SiGe/Si p-n heterojunction materials. Results show that the SiGe alloys crystalline quality and the misfit dislocations are critical influences on the reverse leakage current. The crystal perfection and/or the degree of metastability of the Sice alloys have been estimated in terms of the model proposed by Tsao with the experimental results. High-quality p-n heterojunction diodes can be obtained by optimizing the SiGe alloy structures, which limit the alloys in the metastable states. (C) 1999 Elsevier Science B.V. All rights reserved.

Synthesis and perfection evaluation of NaA zeolite membrane

The synthesis of NaA zeolite membrane on a porous alpha -Al2O3 support from clear solution and the evaluation of the perfection of the as-synthesized membrane by gas permeation were investigated. When an unseeded support was used, the NaA zeolite began to transform into other types of zeolites before a continuous NaA zeolite membrane formed. When the support was coated with nucleation seeds, not only the formation of NaA zeolite on the support surface was accelerated, but also the transformation of NaA zeolite into other types of zeolites was inhibited. A continuous NaA zeolite membrane can be formed. Perfection evaluation indicated that the NaA zeolite membrane with the synthesis time of 3 h showed the best perfection after a one-stage synthesis. The perfection of NaA zeolite membrane can be improved by employing the multi-stage synthesis method. The NaA zeolite membrane with a synthesis time of 2 h after a two-stage synthesis showed the best gas permeation performance, The permselectivity of H-2/n-C4H10 and O-2/N-2 were 19.1 and 1.8, respectively, higher than those of the corresponding Knudsen diffusion selectivity of 5.39 and 0.94, which showed the molecular sieving effect of NaA zeolite. However, the permeation of n-C4H10 also indicated that the NaA zeolite membrane had certain defects, the diameter of which were larger than the NaA zeolite channels. (C) 2001 Elsevier Science B.V. All rights reserved.

Progress In Modeling Of Fluid Flows In Crystal Growth Processes

Modeling of fluid flows in crystal growth processes has become an important research area in theoretical and applied mechanics. Most crystal growth processes involve fluid flows, such as flows in the melt, solution or vapor. Theoretical modeling has played an important role in developing technologies used for growing semiconductor crystals for high performance electronic and optoelectronic devices. The application of devices requires large diameter crystals with a high degree of crystallographic perfection, low defect density and uniform dopant distribution. In this article, the flow models developed in modeling of the crystal growth processes such as Czochralski, ammonothermal and physical vapor transport methods are reviewed. In the Czochralski growth modeling, the flow models for thermocapillary flow, turbulent flow and MHD flow have been developed. In the ammonothermal growth modeling, the buoyancy and porous media flow models have been developed based on a single-domain and continuum approach for the composite fluid-porous layer systems. In the physical vapor transport growth modeling, the Stefan flow model has been proposed based on the flow-kinetics theory for the vapor growth. In addition, perspectives for future studies on crystal growth modeling are proposed. (c) 2008 National Natural Science Foundation of China and Chinese Academy of Sciences. Published by Elsevier Limited and Science in China Press. All rights reserved.

Preliminary-results of gaas single-crystal growth under high gravity conditions

GaAs single crystals have been grown under high gravity conditions, up to 9g0, by a recrystallization method with decreasing temperature. The impurity striations in GaAs grown under high gravity become weak and indistinct with smaller striation spacings. The dislocation density of surcharge-grown GaAs increases with increase of centrifugal force. The cathodoluminescence results also show worse perfection in the GaAs grown at high gravity than at normal earth gravity.