J. A. Van Vechten

Atomic model for the EL0 defect in GaAs

We propose atomic models for the stable and metastable configurations of the bi‐stable, oxygen‐related defect in GaAs known as EL0. They consist of an O on As site donor as a nearest neighbor to a divacancy for the stable configuration and an O on Ga site acceptor between two As vacancies for the metastable configuration. We discuss analogies and distinctions between EL0 and EL2, another important bi‐stable complex. We suggest that this complex is prominent in O‐containing GaAs because divacancies migrate relatively rapidly and so are prone to formation of complexes.

Thermodynamics of Deep Levels in Semiconductor

Thermodynamnies is obviously central to the ultimate goal ol an exquisite control of the electronic properties of scmiconducting devices and to the uinderstanding this will require. It should also be useful for the subsidiary goal of the firm identification of the various electrically active defects. This subsidiary goal will not be achieved unless adequate attention is paid to the reactions among the various atomic and ionization states of the defects, the electrons and the holes.

Effect of Lubricant Environments on Saw Damage in Si Wafers

The effect of lubricant environments on the structure of the surface damage induced in Si during the wafer sawing process was tested for four different lubricants: water, methyl silane solution, Kleenzol B, and dielectric oil. The nature of the saw damage was characterized by transmission electron microscopy and the depth profile of the damage determined by a taper‐sectioning method. The results showed that the number and depth of surface damage is sensitive to the chemical nature of the saw lubricant. Lubricants that are good catalysts for breaking Si bonds can induce more fracture cleavage and produce less surface damage. Lubricants that can dampen more effectively the out‐of‐plane blade vibration can also reduce the surface damage. The chemomechanical effect of the lubricant environment was also tested by applying different potentials on Si crystal during the sawing. Correlation between the applied potential and the depth of damage in the dielectric oil environment was observed and possible mechanisms involved were discussed.

Temperature dependence of the mercury telluride‐cadmium telluride band offset

After reviewing the experimental data on the valence‐band offset for HgTe‐CdTe heterojunctions, we support previous suggestions of an extreme temperature dependence for this offset with a calculation based on a bond charge model. The model predicts the T dependence of the valence‐band offset to be 77% of the difference in the band‐gap temperature dependence of the heterojunction constituents. In the HgTe‐CdTe system, the opposite signs of the band gap T variations yield an anomalously large increase in the offset of 213 meV between 0 and 300 K.

Surface treatment effects on atomic diffusion in Si explained without self interstitials

Many recent discussions of surface treatment effects on atomic diffusion in Si have explained these largely in terms of effects attributed to Si self interstitials. However, we have shown by our straight forward Monte Carlo (VIDSIM) simulation of diffusion of Au into Si according to the “kick-out” mechanism of Seeger that this mechanism is in fact completely incapable of explaining the two-sided, “U shaped” profile of substitutional Au which results from a one sided in-diffusion of Au. We have shown that if Auinterstitials can displace Si at any appreciable rate, then the Au substitutional profile must decrease monotonically from source side to far side. We noted that this is strong evidence that Si self interstitials play no role in thermal processes in Si. Here we show that the surface treatment effects often attributed to Si self interstitials can be naturally explained without them.

Evidence for Ostwald Ripening of Vacancy Clusters in Float Zone Silicon Obtained from Preannealing Dependence of Gold Diffusion Behavior

Part of a float zone Si wafer was given a prolonged anneal at 960°C. Au was then diffused into samples of the annealed and unannealed portions of the wafer for various periods of time. Au concentration was inferred from spreading resistance measurements. We find that the crystal which was annealed before deposition of Au produced a different Au accumulation as a function of time than the as-received crystal. Further, the Au concentration at the center of the wafer does not follow the previously reported t 1/2 behavior ; it follows a curve that exhibits an inflection. We believe these results are best interpreted in terms of vacancy clusters retained in the Si during the original crystal growth.

A simple man's view of the passivation of semiconductors

Abstract The author here attempts to present a fundamental and general discussion of the problem of passivating an electronic device made of semiconducting materials. He also points out what he believes to be a few misconceptions in the current literature and makes a suggestion for further progress.

VIDSIM - A Monte Carlo program for the simulation of atomic diffusion in diamond and zinc-blende structures

Abstract We descibe a Monte Carlo program for the simulation of point defect diffusion interaction in diamond and zinc-blende structure crystals. The simulated defects comprise vacancies, host or impurities. Several diffusion mechanisms, such as vacancy first and second neighbor hopping, the Frank-Turnbull and the kick-out hypothesis are simulated. The program is entirely controlled by the user, who ,ay simulate various models with different parameters, diffusion activation energies, etc. Thus, the evolution of an initial defect configuration - as fed into the program - can be monitored in space and time, giving insight into the simulated model and the relationship between atomic level assumptions and macroscopic observables. The program is suitable to run on microcomputers in background at very low cost and is available to the reader at minimal cost.

On the Origins of Oxidation‐Induced Stacking Faults in Silicon

A qualitative explanation for the origins of oxidation-induced stacking faults, OSFs, is presented. This explanation is based on vacancy annihilation by dislocations during crystal growth, which influences the distribution and size of vacancy clusters within the finished boule. A mechanism for nucleation of OSFs at small clusters of vacancies is described.

Laser-Solid Interactions: Localization of Momentum and of Energy

Mechanisms are discussed by which sufficient momentum and energy may be localized on individual atoms, ions or molecules to account for photoablation in different regimes. In order of increasing excitation intensity, these include the roles of: “recoilless emission” (as in Bragg scattering and the Mossbauer effect) during Auger recombination of a core exciton, particularly in the Knotek-Feibelman effect; the metastable binding of multiple holes earlier proposed by Feibelman, particularly in the data of Itoh and coworkers; the change in the equilibrium interatomic spacing concomitant with excitation of a Frenkel exciton (localized broken bond), particularly in the ablative photodecomposition reported by Srinivasan and co-workers; the interaction of virtual excitons with real excitons in a strongly polarized solid, e.g. one subject to laser annealing pulses; and the interaction of ions with surface plasmons, particularly in the laser sputtering data of Hanabusa et al. A connection is made to rapid annealing and to sub-threshold defect formation. Further support is noted for the bose condensation model of pulsed laser annealing.