Effect of surface stoichiometry on Be doping in GaAs by intermittent supply of AsH3 and TEG in an ultra-high vacuum

The effects of surface stoichiometry on Be doping in GaAs grown by molecular layer epitaxy have experimentally been investigated. Be-doped p⁺-GaAs layers were grown on (0 0 1)-oriented GaAs substrates by intermittent supply of AsH₃ and triethylgallium (TEG) in an ultra-high vacuum. Be(MeCp)₂ was used as a p-type dopant gas. The surface stoichiometry before introducing the dopant gas was controlled by changing the AsH₃ and TEG injection sequence and supply time. The doping characteristics were evaluated by secondary ion mass spectroscopy analysis. It was found that doping characteristics of Be-doped GaAs are strongly dependent on the doping sequence and surface stoichiometry. This experimental result and the Be doping mechanism are discussed on the basis of rate law of the surface chemical reaction.     

In Memoriam

In memoriam Michael John Richardson.     

A 0.5-μm CMOS 4.0-Gbit/s serial link transceiver with datarecovery using oversampling

A 4-Gbit/s serial link transceiver is fabricated in a MOSIS 0.5-μm HPCMOS process. To achieve the high data rate without speed critical logic on chip, the data are multiplexed when transmitted and immediately demultiplexed when received. This parallelism is achieved by using multiple phases tapped from a PLL using the phase spacing to determine the bit time. Using an 8:1 multiplexer yields 4 Gbits/s, with an on-chip VCO running at 500 MHz. The internal logic runs at 250 MHz. For robust data recovery, the input is sampled at 3× the bit rate and uses a digital phase-picking logic to recover the data. The digital phase picking can adjust the sample at the clock rate to allow high tracking bandwidth. With a 3.3-V supply, the chip has a measured bit error rate (BER) of <10^-14     

Novel thermal curing reaction of oxetane resins with polyfunctional phenols

The thermal curing reaction of polyfunctional oxetanes (oxetane resins) such as tris[4‐(3‐ethyloxetane‐3‐yl)methoxyphenyl]methane (TEOMP) and 1,3,5‐tris(3‐ethyl‐3‐oxetanylmethoxy)benzene with certain polyfunctional phenols was performed in bulk with quaternary onium salts as catalysts. The reaction proceeded smoothly at 180–220 °C and produced insoluble gel products, and the rate of gel production increased with the reaction temperature. The rate of the addition reaction of TEOMP with 3,3′,5,5′‐tetrachlorobisphenol A was also measured by IR spectroscopy, and the rate of reaction was proportional to the product of the oxetane concentration and the catalyst concentration in the film state. Furthermore, the glass‐transition temperatures and 5 and 10 wt % weight‐loss temperatures of the resulting gel products were confirmed with differential scanning calorimetry and thermogravimetric analysis, and the glass‐transition temperatures and 5 wt % weight‐loss temperatures were 127–162 °C and 323–351 °C, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2028–2037, 2005     

Aspects of nucleation and drift processes in a one-dimensional model

We introduce a one-dimensional model involving the nucleation and the drift of many particles. The model originates from interacting kink systems and simulates time evolution in modulated systems. In this model the nucleation rate of a particle depends nonlocally on the density of preexisting particles and the drift of particles is due to a weak and repulsive interaction among them. We first study the statistics of this model in the case that the drift of particles is negligible, and then consider the effects of the drift of particles.     

Recent Advance in Terahertz Wave and Material Basis

The unexplored terahertz (THz) region involves important phenomena of both fundamental and applied natures. Examples include phonon interactions, rotational transitions, and intermolecular dynamics. Frequency tunable high-power THz wave generation has been successfully achieved utilizing lattice resonance of LiNbO₃ and GaP crystals, respectively. Semiconductor devices utilizing the electron tunneling effect have also been developed.