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The homoepitaxial growth of 4H-SiC films was conducted on 4H-SiC 150 mm 4° off-axis substrates by using a home-made hot-wall chemical vapor deposition (CVD) reactor. Special attention was paid to the influence of the growth temperature on the surface morphology, growth rate, doping efficiency, and structural uniformity of the films. Among the above factors, growth temperature and flow ratio were shown to be the essential parameters to produce high-quality homoepitaxial layers. Furthermore, a two-side flow tunnel was introduced to control the growth temperature nonuniformity in the reactor. The influence of flow ratio on the epitaxial layer uniformity was also studied. It was found that the surface roughness increased with the increasing temperature, achieving its minimum value of 0.183 nm at 1610 °C. Besides that, the film growth rate decreased with the increase in growth temperature, whereas the degrees of thickness non-uniformity, N2 doping non-uniformity, and doping efficiency increased. Meanwhile, both the thickness and doping uniformity can be improved by adjusting H2 and N2 flow ratios, respectively. In particular, the use of the H2 ratio of 1.63 and N2 ratio of 0.92 enabled one to increase the degree of uniformity of thickness and doping by 0.79% (standard deviation/mean value) and 3.56% (standard deviation/mean value), respectively, at the growth temperature of 1630 °C. [ABSTRACT FROM AUTHOR]

Self‐powered photodetectors that can work without an external power source are expected to play a crucial role in future optoelectronic devices. Herein, SnS2/ZnO1−xSx heterojunctions are fabricated by a facile sputtering method and constructed as self‐powered broadband photodetectors covering from UV (365 nm) to NIR (850 nm). The self‐powered device shows a superior responsivity of 8.28 mAW−1, a photodetectivity of 5.09 × 1010 Jones, and a high Ion/Ioff ratio of 1.08 × 105 at 365 nm. Furthermore, the SnS2/ZnO0.7S0.3 heterojunction device presents a fast response speed with a rise time of 49.51 ms and a decay time of 25.93 ms. The high performance of the device is attributed to the type II band alignment of the heterojunction as well as the Schottky barrier. The high responsivity, fast response speed, large Ion/Ioff ratio, and broadband response enable the SnS2‐based heterojunction a potential candidate for self‐powered photodetectors in the range from UV to NIR. [ABSTRACT FROM AUTHOR]

SUMMARY In this paper, we consider amplify-and-forward multiple-input multiple-output multiple-relay systems, where all the nodes have multiple antennas. For enhancing link reliability, we address the problem of designing optimal linear transceiver to minimize the mean squared error (MSE) of symbol estimations subject to the total relay transmit power constraint. This problem is highly complex and has not been solved in the literature. We first simplify this optimization problem to one that takes a singular value vector and a unitary matrix as optimization variables. Then based on the analyses for the simplified problem, we develop an iterative algorithm consisting of one boundary optimization and one unitary matrix constrained optimization. We show analytically that the proposed iterative algorithm always converges, and the MSE is monotonically decreasing from one iteration to the next. Finally, numerical results demonstrate the nearly optimal performance of the proposed scheme. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]