Naoto Yoshimoto

Microtwin formation in gallium arsenide by iron ion implantation and amorphization by annealing

Cross‐sectional views of iron ion‐implanted gallium arsenide to doses of 4×1014 cm−2 and 1×1015 cm−2 were observed by transmission electron microscopy before and after annealing at 673 K. Microtwins were formed below the surface by implantation of 4×1014 ions cm−2. In the sample implanted to the dose of 1×1015 cm−2 , the region below the surface was amorphized and a thin microtwin layer was observed between the amorphous layer and the crystalline matrix. The electron diffraction pattern and the high‐resolution multibeam lattice image showed that the structure of the microtwin is an atomic stacking of ABCA‘CB‘ABC along the 〈111〉 direction. In both samples, the microtwin layer transformed to the amorphous structure by annealing at 673 K for 30 min. It is suggested that the behavior in gallium arsenide implanted with iron, which is much different from that implanted with the other ion species, may be attributed to the coordination number of the covalent bonding iron.

Amorphization and solid-phase epitaxial growth in tin-ion-implanted gallium arsenide

The amorphization and recrystallization of tin‐ion‐implanted gallium arsenide were studied by cross‐sectional transmission electron microscopy. Amorphization occurred in the sample implanted at a dose of 1014 ions/cm2. The interface between the amorphous region and the crystalline matrix is not flat. The amorphous region recrystallizes epitaxially with microtwin formation at 673 K. The amorphous‐crystalline interface in the sample implanted at a dose of 1016 ions/cm2 is flat. In the deep region of this sample a solid‐phase epitaxial growth without microtwin formation is observed after annealing at 673 K. These structural changes were compared with the nuclear energy loss (damage energy) distribution simulated by the trim code. It is concluded that the amorphization of the sample implanted at a dose of 1014 ions/cm2 is induced by the accumulation of damage energy; on the other hand, the amorphization of the sample implanted at a dose of 1016 ions/cm2 cannot be explained only by this process. The contributi...

Synthetic traffic generation for streaming video to model IPTV

With the rapid development of access networks, Internet Protocol Television (IPTV) has become a popular streaming video delivery technology. However, streaming IPTV over a network is challenging as the data rate of a video streaming varies with scene, time, frame-rate, and encoding. As a result, it is important to evaluate the performance of an access network for IPTV traffic to ensure better experience for users. Using video traces for such evaluation requires different videos traces to represent different scenarios and needs slower I/O-based operations, such as file reading. To overcome these limitations, in this paper, we explore several aspects of modeling IPTV streaming and present a synthetic video trace generator that represents the IPTV streaming. Our analysis shows that our synthetic video trace follows the statistical properties of empirical videos and its resultant data rate is representative of the IPTV video streaming.

Low latency dynamic bandwidth allocation for 100km long reach 10G-EPON

We propose a new dynamic bandwidth allocation (DBA) method for long reach passive optical networks (PON) that can shorten upstream latency. In this method, the OLT allocates bandwidth to long-distance (up to 100 km) ONUs preliminarily and shortens the latency of long-distance optical network units (ONUs). This has no influence on the latency of short-distance ONUs if they coexist with long-distance ONUs. We show that this new DBA method achieves a smaller latency with long-distance ONUs than the conventional DBA technique, and that there is no influence on short-distance ONUs.